- 1 FLUID MACHINE CROSS-REFERENCE TO RELATED APPLICATIONS This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2010 5 204824, filed on September 13, 2010 and Japanese Patent Application No. 2011-162187, filed on July 25, 2011; the entire contents of which are incorporated herein by reference. TECHNICAL FIELD 10 Embodiments described herein relate generally to a fluid machine such as a Francis-type turbine and a Francis-type pump-turbine. BACKGROUND As a fluid machine, there are, for example, types 15 such as a hydro turbine, a pump and the like. For example, the fluid machine such as a Francis-type turbine has a rotating portion and a stationary portion, so that there occurs a leakage flow that is part of the working fluid flowing through the gap between them. The leakage 20 flow does not perform energy exchange with a prime mover within the fluid machine, and a leakage loss is caused depending on a flow rate of the leakage flow. Therefore, to reduce the flow rate of the leakage flow as small as possible, a seal structure formed of a minimum gap is 25 adopted in the vicinity of the inlet and outlet of the fluid machine. In addition to the structure configured of only the minimum gap, this seal structure includes a structure that the passage is narrowed by forming a projection of a 30 rectangular shape, a saw-tooth shape or a thread shape from, for example, a sealing surface of the stationary portion, at a part of the gap between the stationary portion and the rotating portion configuring a sealing 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 2 portion, and a structure that the sealing portion is formed to have multiple stages. The hydro turbine such as a Francis-type turbine uses river water containing earth and sand as a working fluid. 5 Therefore, for example, a conventional seal structure that a passage is narrowed by forming a projection from a sealing surface of the stationary portion suffers from abrasion of the tip end of the projection due to river water containing earth and sand, resulting in a 10 possibility that a sealing effect is deteriorated, and a flow rate of the leakage flow of the working fluid (river water) increases. SUMMARY OF THE DISCLOSURE In a first aspect of the invention there is provided 15 a fluid machine provided with a sealing portion formed of an annular minute gap between a rotating portion which is provided with a plurality of blades and an annular member disposed circumferentially at one ends of the blades and a stationary portion which is arranged in opposition to the 20 annular member. A groove portion having a cross-sectional shape of an n-angled shape (n=3 or more) is circumferentially formed on a wall portion of the annular member or the stationary portion which configures the sealing portion. An angle 0, which is formed between a 25 side WO of the groove portion on an extended line of a wall surface of the wall portion and a side WU of the groove portion on the most upstream side with respect to a flowing direction of a leakage flow, is 150 or more and 40 or less in a cross section perpendicular to a groove 30 forming direction of the groove portion. In some embodiments, an angle a may be formed between a side WD on the most downstream side with respect to the flowing direction of the leakage flow and the side WO in the cross section of the groove portion, is 900 or less. 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 3 In some embodiments, the side WU may be determined to have a length Lwu, and a value LwusinO is not smaller than a width value of the minute gap between the annular member and the stationary portion. 5 The groove portion may have an n-angled shape (n=4 or more) in a cross-sectional shape, a side W1 adjacent to the side WU is parallel to the side WO. An end portion where a wall surface on the most upstream side of the groove portion, which may be 10 equivalent to the side WU in the cross section, and a wall surface of the wall portion adjacent to the most upstream side wall surface are contacted is formed into an arc shape. The groove portion may be formed into a horizontal 15 annular shape and in at least one stage in a direction of a rotating shaft. The groove portion may be formed helically at an inclination angle O with respect to a horizontal direction and in at least one stage in the direction of the rotating shaft. Furthermore, one end of 20 the groove portion may be located on an outlet side than on an inlet side of the sealing portion, and the other end of the groove portion is located on the inlet side than on the outlet side of the sealing portion. A convex wall surface having a curvature radius not 25 smaller than a width value of the minute gap between the annular member and the stationary portion may be formed instead of the wall surface equivalent to the side WU. In a second aspect of the invention, there is provided a fluid machine provided with a sealing portion 30 which is formed of an annular minute gap between a rotating portion provided with a plurality of blades and an annular member disposed circumferentially at one ends of the blades and a stationary portion arranged in opposition to the annular member, wherein a wall portion 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 of the annular member or the stationary portion configuring the sealing portion has at least one groove portion circumferentially which is formed of a shape having one curve ZO along the surface of the wall portion 5 and at least two sides in a horizontal cross section; and an angle y, which is formed between a side ZU of the groove portion on the most upstream side with respect to a flowing direction of a leakage flow flowing circumferentially in the horizontal cross section and a 10 tangent to the curve ZO at an intersection of the end portion on the upstream side of the side ZU with the curve ZO, is in a range of 150 or more and 400 or less. An angle 6 may be formed between a side ZD configuring the groove portion on the most downstream side with 15 respect to the flowing direction of the leakage flow, and a tangent to the curve ZO at an intersection of the end portion on the downstream side of the side ZD and the curve ZO, and maybe 900 or less. The length of the side ZU may be determined to be Lzu, 20 a length of a normal line drawn from one end of the side ZU at the back of the groove to the curve ZO is not less than the width of the minute gap between the annular member and the stationary portion. A portion where a wall surface on the most upstream 25 side of the groove portion equivalent to the side ZU in the horizontal cross section and a wall surface of the wall portion adjacent to the most upstream-side wall surface are contacted, may be formed into an arc shape. One end of the groove portion may be located on an 30 outlet side than on an inlet side of the sealing portion, and the other end of the groove portion is located on the inlet side than on the outlet side of the sealing portion. A convex wall surface having a curvature radius not smaller than a width value of a minute gap between the 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 5 annular member and the stationary portion may be formed instead of the wall surface equivalent to the side ZU. BRIEF DESCRIPTION OF THE DRAWINGS 5 Fig. 1 is a view showing a part of a hydro turbine of a first embodiment of the invention in a meridional cross section. Fig. 2 is a view showing a meridional cross section of a seal structure provided to the hydro turbine of the 10 first embodiment. Fig. 3 is a view of a meridional cross section showing in a magnified fashion a groove portion of the seal structure provided to the hydro turbine of the first embodiment. 15 Fig. 4 is a view of a meridional cross section showing in a magnified fashion an alternative shape of the groove portion of the seal structure provided to the hydro turbine of the first embodiment of the invention. Fig. 5 is a view of a meridional cross section 20 showing in a magnified fashion a groove portion of a seal structure provided to the hydro turbine in accordance with a second embodiment of the invention. Fig. 6 is a view of a meridional cross section showing in a magnified fashion an alternative shape of the 25 groove portion of the seal structure provided to the hydro turbine of the second embodiment of the invention. Fig. 7 is a plan development view of grooves formed on a surface of a sealing liner of the hydro turbine of a third embodiment of the invention as viewed from a runner 30 band side. 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 6 Fig. 8 is a view showing a meridional cross section of a seal structure provided to the hydro turbine of a fourth embodiment of the invention. Fig. 9 is a view showing a part of a cross section 5 taken along line A-A of Fig. 8. Fig. 10 is a view showing a horizontal cross section of a part of a groove portion of a seal structure provided to the hydro turbine of a fifth embodiment of the invention. 10 Fig. 11 is a view showing in a magnified fashion a meridional cross section of a groove portion of a sealing portion having a conventional groove. Fig. 12 is a view showing losses determined by numerical analysis of flows. 15 Fig. 13 is a view showing the condition of a flow in a groove portion of the sealing portion according to the fifth embodiment of the invention. Fig. 14 is a view showing the condition of a flow in the groove portion of a sealing portion of a conventional 20 hydro turbine. Fig. 15 is a view showing in a magnified fashion a meridional cross section of a sealing portion according to the first embodiment. Fig. 16 is a view showing in a magnified fashion a 25 meridional cross section of a sealing portion of a conventional hydro turbine. Fig. 17 is a view showing the results of measuring discharge factors of leakage flows. DETAILED DESCRIPTION 30 Embodiments of the invention are described below with reference to the drawings. 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 7 Fig. 1 is a view showing a part of a hydro turbine 10 in accordance with a first embodiment in a meridional cross section. As an example of the hydro turbine 10 which functions as a fluid machine, a Francis-type turbine 5 is described below. Like component parts in the following embodiments are denoted by like reference numerals, and overlapped descriptions will be omitted or simplified. As shown in Fig. 1, a Francis-type runner 12 is connected to the bottom end of a main shaft 11 of the 10 hydro turbine 10. A generator (not shown in the Figures) is connected to the top of the main shaft 11. The runner 12 includes plural runner blades 13 which are arranged at prescribed intervals circumferentially, a disc-shaped crown 14 which fixes the runner blades 13 from their one 15 sides, and a runner band 15 which functions as an annular member to fix the runner blades 13 from the other sides. The crown 14 is connected to the main shaft 11. A casing 16 is arranged on an outer periphery of the runner 12, and plural stay vanes 17 are arranged 20 circumferentially on an inner peripheral portion of the casing 16. A plurality of guide vanes 18 are arranged circumferentially between the stay vanes 17 and the runner 12. A cover 19 is disposed above the runner 12, and a 25 discharge ring 20 is disposed below the runner 12. In addition, a draft tube 21, which is connected to a discharge ring 20, is disposed below the runner 12. A seal structure is configured between the runner band 15 of the runner 12 configuring a rotating portion 30 and a stationary portion such as the discharge ring 20 disposed in opposition to the runner band 15 to surround the runner band 15. The seal structure is described below. 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 8 Fig. 2 is a view showing a meridional cross section of the seal structure provided to the hydro turbine 10 of the first embodiment. Fig. 3 is a view of a meridional cross section showing in a magnified fashion a groove 5 portion of the seal structure provided to the hydro turbine 10 of the first embodiment. Fig. 4 is a view of a meridional cross section showing in a magnified fashion another shape of the groove portion of the seal structure provided to the hydro turbine 10 of the first embodiment. 10 As shown in Fig. 2, a sealing portion 31 which is formed of an annular minute gap and an annular gap portion 33 which is communicated with a main passage 35 and allows to flow a main flow bent at right angles from an outlet 32 of the sealing portion 31 are configured between the 15 runner band 15 and a sealing liner 22 which is a stationary portion formed on a surface of the discharge ring 20 so as to be opposite to the runner band 15. The annular gap portion 33 is bent at right angles from the outlet 32 of the sealing portion 31 here but it is 20 determined that the bent angle (bent angle of the portion whose surface is bent into an L-shape in the sealing liner 22 shown in Fig. 2) includes a range of 60 to 1200. The bent angle is determined to fall in the above range because, for example, a vertical axis-type Francis-type 25 turbine has a possibility of placing the runner 12 on a surface 23 of the sealing liner 22 configuring the gap portion 33 at the time of assembling and disassembling, and if the bent angle is not in the above range, it is difficult to place the runner 12 on the surface 23, and it 30 is not realistic. As shown in Fig. 2 and Fig. 3, a horizontal annular groove 40 is formed circumferentially on a surface 24 of the sealing liner 22 configuring the sealing portion 31. Thus, the groove 40 is positioned between an inlet 34 and 35 the outlet 32 of the sealing portion 31. 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 9 The groove 40 has a quadrangular shape in a meridional cross section perpendicular to the formed direction of the groove 40. The shape of the groove 40 in the meridional cross section is not limited to the 5 quadrangular shape but may be an n-angled shape (where n=3 or more) such as a triangular shape, a pentagonal shape or the like. Fig. 4 shows a case that the groove 40 in a meridional cross section is triangular. As shown in the meridional cross section of Fig. 3, 10 it is determined that an angle 0 formed between a side WU of the groove 40, which is on the most upstream side with respect to a flowing direction of a leakage flow (direction of the arrow shown in Fig. 3), and a side WO of the groove 40, which is on an extended line of the surface 15 24 of the sealing liner 22, is in a range of 150 or more and 400 or less. When it is configured to have the angle 0 in the range of 150 or more and 400 or less, a moderate expansion in the cross-section of the passage while the leakage flow which 20 has flowed into the sealing portion 31 flows through the passage cross section of the sealing portion 31 where the groove 40 is formed. Therefore, the leakage flow does not separate from the wall surface equivalent to the side WU but expands while being decelerated along the wall 25 surface, and part of the leakage flow having flowed into the groove 40 suffers loss due to collision, friction with the wall surface and the like. Meanwhile, when the angle 0 is less than 150, the depth of the groove 40 is small, and the above-described effect is not exerted. Accordingly, 30 when the angle 0 exceeds 400 the leakage flow flows without flowing into the groove 40. In the meridional cross section, it is preferable to configure that an angle a which is formed between a side WD of the groove 40 on the most downstream side with 35 respect to the flowing direction of the leakage flow and 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 10 the side WO is 90 or less. When the angle a exceeds 900, a stagnation region is formed in the vicinity of an end portion where the wall surface equivalent to the side WD and the wall surface equivalent to a side W1 adjacent to 5 the side WD are contacted. The lower limit value of the angle a of the groove 40 is preferably about 600 in terms of configuring the length in the direction of the rotating shaft to an appropriate length. When it is determined that the side WU has a length 10 Lwu in the meridional cross section, it is preferable that a value LwusinO, namely a distance N (length of a straight line which intersects at right angles from one end of the side WU to the side WO) from one end of the side WU at the back of the groove to the side WO, is not less than a 15 width M of the minute gap between the runner band 15 and the sealing liner 22. When the value LwusinO (distance N) is determined to be not less than the width M, a flow velocity of the leakage flow in the passage cross section of the sealing portion 31, where the groove 40 is formed, 20 can be decelerated to about 1/2. As shown in Fig. 3, when it is determined that the groove 40 in the meridional cross section has a quadrangular shape, it is preferable that the side W1 adjacent to the side WU becomes parallel to the side WO. 25 The same is also applied when the shape of the groove 40 in the meridional cross section has an n-angled shape (n=5 or more). By configuring the wall surface equivalent to the side W1 as described above, the passage cross section of the sealing portion 31 becomes constant when the 30 leakage flow flows along the side W1, so that the leakage flow is suppressed from separating from the wall surface equivalent to the side W1. The loss of the leakage flow due to the friction with the wall surface in the groove 40 can be increased. An angle 6 formed between the side WU 35 and the side W1 in the meridional cross section is preferably set to about 140 to 1700 to make the passage 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 11 cross section constant or to expand the passage cross section moderately so as to decrease the flow velocity. Here, an end portion where a wall surface on the most upstream side of the groove 40, which is equivalent to the 5 side WU in a meridional cross section, and the surface 24 of the sealing liner 22 adjacent to the wall surface are contacted may be formed into an arc shape (R portion). By configuring in this way, the leakage flow flowing into the groove 40 can be prevented from separating at a start 10 position of the wall surface equivalent to the side WU. Therefore, part of the leakage flow can be flowed into the groove 40 securely, and the loss in the groove 40 can be increased. Subsequently, the action of the working fluid in the 15 hydro turbine 10 and the sealing portion 31 is described below with reference to Fig. 1 to Fig. 3. Pressurised water, which is a working fluid introduced from an upper reservoir through an iron pipe, flows through the casing 16 and the stay vanes 17 and is 20 introduced into the runner 12 through the guide vanes 18 where the flow rate is adjusted. In the runner 12, pressure energy of the introduced pressurised water is converted into rotation energy. The runner 12 rotates around the main shaft 11 which is a rotating shaft, and a 25 generator (not shown in the Figures) coupled with the main shaft 11 is rotated to generate electricity. The working fluid having flowed through the runner 12 is discharged to a lower reservoir on a downstream side through the draft tube 21. 30 Meanwhile, the leakage flow having flowed between the runner band 15 and the discharge ring 20 flows into the sealing portion 31. When the leakage flow having flowed into the sealing portion 31 flows through a passage cross section of the sealing portion 31 where the groove 40 is 35 formed, a passage cross-sectional area expands moderately. 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 12 Therefore, the leakage flow does not separate from the wall surface equivalent to the side WU but expands while being decelerated along the wall surface, and part of the leakage flow having flowed into the groove 40 suffers loss 5 due to collision, friction with the wall surface and the like. The leakage flow having flowed through the passage cross section, where the groove 40 is formed, flows through the passage (minute gap of the width M between the runner band 15 and the sealing liner 22) of the sealing 10 portion 31 whose passage cross-sectional area is decreased. At this time, the flow is narrowed down, and a loss is generated due to a contracted flow. The leakage flow having passed through the sealing portion 31 is ejected at a high velocity from the outlet 15 32 of the sealing portion 31 to the gap portion 33, flows through the gap portion 33, and leads out to the main passage 35. As described above, when the groove 40 having the above prescribed shape is formed on the wall surface of 20 the passage configuring the sealing portion 31 according to the hydro turbine 10 of the first embodiment, the loss due to friction and the like can be increased while the leakage flow flows through the passage cross section where the groove 40 is formed. In addition, the leakage flow 25 having flowed through the passage cross section where the groove 40 is formed has the generation of loss due to the contracted flow. Thus, the leakage flow suffers the loss in the sealing portion 31, and the loss is larger than that generated when the groove 40 is not formed. 30 Therefore, since the loss in the sealing portion 31 is large according to the hydro turbine 10 of the first embodiment, the sealing effect is high, the flow rate of the leakage flow can be reduced, and the volumetric efficiency of the hydro turbine 10 can be improved. 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 13 In the above example, the annular groove 40 which is horizontal and circumferentially formed on the surface 24 of the sealing liner 22 between the inlet 34 and the outlet 32 of the sealing portion 31 is provided in a 5 single stage, but the groove 40 may be provided in plural stages with prescribed intervals in the direction of the rotating shaft. The same action and effect as those described above can be obtained. In the above example, the groove 40 is provided on 10 the surface 24 of the sealing liner 22 which is a stationary portion, but the groove 40 may also be formed on the surface of the runner band 15 which is a rotating portion configuring the sealing portion 31. The same action and effect as those described above can also be 15 obtained. In a second embodiment of the invention, a hydro turbine 100 is provided which is different from the hydro turbine 10 of the first embodiment on the point that the sealing portion 31 has a different groove shape, and 20 therefore, the description will mainly focus on the groove shape. Fig. 5 is a view of a meridional cross section showing in a magnified fashion a groove portion of a seal structure provided to the hydro turbine 100 of the second 25 embodiment. Fig. 6 is a view of a meridional cross section showing in a magnified fashion another shape of the groove portion of the seal structure provided to the hydro turbine 100 of the second embodiment. As shown in Fig. 5, an annular groove 50 which is 30 horizontal and circumferentially formed on the surface 24 of the sealing liner 22 which configures the sealing portion 31. Thus, the groove 50 is located between the inlet 34 and the outlet 32 of the sealing portion 31. 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 14 The groove 50 has in a meridional cross section a substantially quadrangular shape which has the most upstream side of the groove 50 formed into a convex curve WU2 in the flowing direction (direction of the arrow shown 5 in Fig. 5) of the leakage flow. Thus, the second embodiment has a wall surface equivalent to the curve WU2 instead of the wall surface equivalent to the side WU of the groove 40 of the sealing portion 31 of the hydro turbine 10 of the first embodiment. 10 The shape of the groove 50 in the meridional cross section may be a substantially n-angled shape (n=3 or more) such as a substantially triangular shape, a substantially pentagonal shape or the like if the most upstream side has the convex curve WU2 in the flowing 15 direction (direction of the arrow shown in Fig. 5) of the leakage flow. Fig. 6 shows that the groove 50 in a meridional cross section has a substantially triangular shape. It is preferable that the curve WU2 has a curvature 20 radius of not less than the width M of the minute gap between the runner band 15 and the sealing liner 22 so to moderately expand the passage cross-sectional area in the inflow portion of the groove 50. In the meridional cross section, it is preferable 25 that a distance P (length of a straight line which intersects at right angles from one end of the curve WU2 to the side WO) from one end of the curve WU2 at the back of the groove to the side WO is not less than the width M of the minute gap between the runner band 15 and the 30 sealing liner 22. When the distance P is determined to be not less than the width M, a flow velocity of the leakage flow in the passage cross section of the sealing portion 31, where the groove 50 is formed, can be decelerated to about 1/2. 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 15 As shown in Fig. 5, when the shape of the groove 50 in the meridional cross section is determined to have a substantially quadrangular shape, it is preferable that the side W1 adjacent to the curve WU2 becomes parallel to 5 the side WO. The same is also applied when the shape of the groove 50 in the meridional cross section has an n angled shape (n=5 or more). By configuring the wall surface equivalent to the side W1 as described above, the passage cross section of the sealing portion 31 becomes 10 constant when the leakage flow flows along the side W1, so that the leakage flow is suppressed from separating from the wall surface equivalent to the side W1. The loss of the leakage flow due to the friction with the wall surface in the groove 50 can be increased. 15 As described above, since the moderate expansion of the cross-sectional area of the passage an inflow portion of the groove 50 of the hydro turbine 100 of the second embodiment, the leakage flow does not separate from the wall surface equivalent to the curve WU2 but expands while 20 being decelerated along the wall surface. The part of the leakage flow having flowed into the groove 50 suffers loss due to collision, friction with the wall surface and the like. Thus, the sealing effect can be enhanced by increasing the loss in the sealing portion 31 by the hydro 25 turbine 100 of the second embodiment. Thus, the flow rate of the leakage flow can be decreased, and the volumetric efficiency of the hydro turbine 100 can be improved. In the above example, the annular groove 50 which is horizontal and circumferentially formed on the surface 24 30 of the sealing liner 22 between the inlet 34 and the outlet 32 of the sealing portion 31 is provided in a single stage, but the groove 50 may be provided in plural stages with prescribed intervals in the direction of the rotating shaft. The same action and effect as those 35 described above can be obtained. 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 16 In the above example, the groove 50 is provided on the surface 24 of the sealing liner 22 which is a stationary portion, but the groove 50 may be formed on the surface of the runner band 15 which is a rotating portion 5 configuring the sealing portion 31. The same action and effect as those described above can also be obtained. A hydro turbine 101 according to a third embodiment of the invention has a groove which is formed helically on the surface 24 of the sealing liner 22 or the surface of 10 the runner band 15, instead of the annular grooves 40 and 50 of the sealing portion 31 in the hydro turbine 10 of the first embodiment and the hydro turbine 100 of the second embodiment. Fig. 7 is a plan development view of the grooves 15 formed on the surface 24 of the sealing liner 22 of the hydro turbine 101 of the third embodiment viewed from the side of the runner band 15. The arrow shown in Fig. 7 indicates a rotating direction of the rotating portion. As shown in Fig. 7, the grooves 40 and 50 are 20 inclined downward at an angle O with respect to the horizontal direction and the rotating direction of the rotating portion and formed helically in the direction of the rotating shaft on the surface 24 of the sealing liner 22. The angle 0 is set to be larger than 00, and 25 preferably set to about 10 to 450 considering an influence of the flow of the leakage flow. The grooves 40 and 50 are appropriate when they are provided in at least one stage with prescribed intervals in the direction of the rotating shaft and may also be 30 provided in plural stages in the direction of the rotating shaft as shown in Fig. 7. In this example, the grooves 40 and 50 are formed on the surface 24 of the sealing liner 22, but the grooves 40 and 50 may be formed on the surface 24 of the runner band 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 17 15 which is the rotating portion. Even when the grooves 40 and 50 are formed on the surface 24 of the runner band 15, the grooves 40 and 50 are formed to incline downward at an angle O with respect to the horizontal direction and 5 the rotating direction of the rotating portion similar to the formation of the grooves 40 and 50 on the surface 24 of the sealing liner 22. The shapes of the grooves 40 and 50 are similar to those of the grooves 40 and 50 in the above-described first and second embodiments. Namely, the 10 shape of the groove of the third embodiment shown in a cross section perpendicular to the inclined direction (groove forming direction) of the angle 0 is similar to the shapes of the grooves in the meridional cross section described in the first and second embodiments. 15 It is also configured that the end portions on the upstream sides of the grooves 40 and 50 are located on the side of the outlet 32 than on the side of the inlet 34 of the sealing portion 31, and the end portions on the downstream sides of the grooves 40 and 50 are located on 20 the side of the inlet 34 than on the side of the outlet 32 of the sealing portion 31. Accordingly, the leakage flow does not flow from the upstream side of the sealing portion 31 directly into the grooves 40 and 50, while the leakage flow does not flow from the grooves 40 and 50 25 directly into the gap portion 33. In this embodiment, the leakage flow flows through the sealing portion 31 while swirling due to an influence of the friction on the surface of the runner band 15. For example, when the groove 40 is formed horizontally as in 30 the first embodiment, the real angle of the leakage flow with respect to a side WO becomes not more than the angle 0 of the side WU with respect to the side WO of the groove 40 when viewed along the flowing direction of the leakage flow. However, when the groove 40 is formed such as to 35 incline downward at the angle O with respect to the horizontal direction and the rotating direction of the 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 18 rotating portion as in the third embodiment, the real angle of the leakage flow with respect to the side WO becomes smaller than the angle in the case that the above described groove 40 is formed horizontally. Therefore, 5 when the leakage flow flows into the grooves 40 and 50, it does not separate from the wall surface equivalent to the side WU and the curve WU2 but expands while being decelerated along the wall surface. Part of the leakage flow having flowed into the grooves 40 and 50 suffers loss 10 due to collision, and friction with the wall surface and the like. Thus, the sealing effect can be enhanced by increasing the loss in the sealing portion 31 by the hydro turbine 101 of the third embodiment. Therefore, the flow rate of the leakage flow can be decreased, and the 15 volumetric efficiency of the hydro turbine 101 can be improved. In a fourth embodiment according to the invention, there is provide a hydro turbine 102 having a groove on the surface 24 or the sealing liner 22 or the surface of 20 the runner band 15 in the direction of the rotating shaft. Fig. 8 is a view showing a meridional cross section of a seal structure provided to the hydro turbine 102 of the fourth embodiment according to the invention. Fig. 9 is a view showing a part of cross section A-A of Fig. 8. 25 As shown in Fig. 8 and Fig. 9, the sealing portion 31 formed of an annular minute gap and the annular gap portion 33, where the main stream bent at right angles from the outlet 32 of the sealing portion 31 flows and which is communicated with the main passage 35, are 30 configured between the runner band 15 of the runner 12 configuring the rotating portion and the sealing liner 22 as the stationary portion which is arranged on a surface of the discharge ring 20 so as to be opposite to the runner band 15. 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 19 A groove 60 is formed in the direction of the rotating shaft on the surface 24 of the sealing liner 22 configuring the sealing portion 31. As shown in Fig. 8, it is configured that the end portion on the upstream side 5 of the groove 60 is located on the side of the outlet 32 than on the side of the inlet 34 of the sealing portion 31, and the end portion on the downstream side of the groove 60 is located on the side of the inlet 34 than on the side of the outlet 32 of the sealing portion 31. 10 Thus, the leakage flow does not flow from the upstream side of the sealing portion 31 directly into the groove 60, while the leakage flow does not flow from the groove 60 directly into the gap portion 33. As shown in Fig. 9, the groove 60 has a substantially 15 quadrangular shape that is formed to have a curve ZO along the surface 24 of the sealing liner 22 and three sides ZU, ZD and Z1 in a horizontal cross section. The shape of the groove 60 in the horizontal cross section is not limited to the substantially quadrangular shape but may be 20 substantially triangular which is formed to have the curve ZO and two sides ZU and ZD, or substantially polygon which is formed to have the curve ZO and four or more sides. The groove 60 is appropriate when at least one side is formed circumferentially and may be provided 25 circumferentially as a plurality of grooves with prescribed intervals therebetween as shown in Fig. 9. As shown in the horizontal cross section of Fig. 9, it is configured that an angle y, which is formed between the side ZU of the groove 60 on the most upstream side 30 with respect to the flowing direction (direction of the arrow in Fig. 9) of the leakage flow and a tangent to the curve ZO at an intersection of the end portion on the upstream side of the side ZU with the curve ZO, is in a range of 150 or more and 400 or less. 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 20 When it is configured that the angle y is in a range of 150 or more and 400 or less, the passage cross-sectional area expands moderately while the leakage flow having flowed into the sealing portion 31 flows through the 5 passage cross section of the sealing portion 31 where the groove 60 is formed. Therefore, the leakage flow does not separate from the wall surface equivalent to the side ZU but expands while being decelerated along the wall surface, and part of the leakage flow having flowed into 10 the groove 60 suffers loss due to collision, friction with the wall surface and the like. When the angle y is less than 150, the depth of the groove 60 is small, and the above-described effect is not exerted. When the angle y exceeds 400 the leakage flow flows through without entering 15 the groove 60. In the groove 60 of the horizontal cross section, it is preferable to configure that an angle 6, which is formed between the side ZD on the most downstream side with respect to the flowing direction of the leakage flow and a 20 tangent to the curve ZO at an intersection of the end portion at the downstream side of the side ZD and the curve ZO, becomes 900 or less. When the angle 6 exceeds 900, a stagnation region is formed in the vicinity of the end portion where the wall surface equivalent to the side 25 ZD and the wall surface equivalent to the side Z1 adjacent to the side ZD are contacted. It is preferable that the lower limit value of the angle 6 is determined to be about 600 from the viewpoint that the length (namely, length equivalent to the curve ZO) of the groove 60 in a 30 circumferential direction is determined to be appropriate. When the length of the side ZU is determined to be Lzu in the horizontal cross section, it is preferable that a length Q of the normal line drawn from one end of the side ZU at the back of the groove to the curve ZO is not less 35 than the width M of the minute gap between the runner band 15 and the sealing liner 22. When the length Q of the 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 21 normal line is determined to be not less than the width M, a flow velocity of the leakage flow in the passage cross section of the sealing portion 31, where the groove 60 is formed, can be decelerated to about 1/2. 5 When the shape of the groove 60 in the horizontal cross section is determined to be a substantially quadrangular shape, the side Z1 adjacent to the side ZU may be formed as a curve which becomes concentric with the curve ZO. By configuring in this way, when the leakage 10 flow flows along the curve which becomes concentric with the curve ZO, the passage cross section of the sealing portion 31 becomes constant, and the leakage flow is suppressed from separating from the wall surface equivalent to this curve. The loss of the leakage flow 15 due to the friction with the wall surface in the groove 60 can be increased. Here, an end portion where a wall surface on the most upstream side of the groove 60, which is equivalent to the side ZU in a horizontal cross section, and the surface 24 20 of the sealing liner 22 adjacent to the wall surface are contacted may be formed into an arc shape (R portion). By configuring in this way, the leakage flow flowing into the groove 60 can be prevented from separating at a start position of the wall surface equivalent to the side ZU. 25 Therefore, part of the leakage flow can flow into the groove 60 securely, and the loss in the groove 60 can be increased. As described above, when the groove 60 having the above prescribed shape is formed on the wall surface of 30 the passage configuring the sealing portion 31 according to the hydro turbine 102 of the fourth embodiment, the loss due to friction and the like can be increased while the leakage flow flows through the passage cross section where the groove 60 is formed. In addition, the leakage 35 flow having flowed through the passage cross section where 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 22 the groove 60 is formed has the generation of loss due to the contracted flow. Thus, the leakage flow suffers the loss in the sealing portion 31, and the loss is larger than that generated when the groove 60 is not formed. 5 Therefore, since the loss in the sealing portion 31 is large according to the hydro turbine 102 of the fourth embodiment, the sealing effect is high, the flow rate of the leakage flow can be decreased, and the volumetric efficiency of the hydro turbine 102 can be improved. 10 In the above example, the groove 60 is provided on the surface 24 of the sealing liner 22 which is a stationary portion, but the groove 60 may be formed on the surface of the runner band 15 which is a rotating portion configuring the sealing portion 31. In the example here, 15 a groove 60 is configured to have a continuous groove structure along the direction of the rotating shaft, but the groove 60 may be provided intermittently along the direction of the rotating shaft, namely, a plurality of grooves 60 may be provided with prescribed intervals along 20 the direction of the rotating shaft. In the above examples, the same action and effect as those described above can also be obtained. According to a fifth embodiment of the invention, there is provided a hydro turbine 103 of a fifth 25 embodiment is different from the hydro turbine 102 of the fourth embodiment on the point that the sealing portion 31 has a different groove shape. Therefore, the groove shape is mainly described below. Fig. 10 is a view showing a horizontal cross section 30 of a part of a groove portion of a seal structure provided to the hydro turbine 103 of the fifth embodiment. As shown in Fig. 10, grooves 70 are formed along the direction of the rotating shaft on the surface 24 of the sealing liner 22 configuring the sealing portion 31. It 35 is configured that the end portion on the upstream side of 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 23 the groove 70 is located on the side of the outlet 32 (See Fig. 8) rather than on the side of the inlet 34 (See Fig. 8) of the sealing portion 31, and the end portion on the downstream side of the groove 70 is located on the side of 5 the inlet 34 rather than on the side of the outlet 32 of the sealing portion 31. The groove 70 in the horizontal cross section has a substantially quadrangular shape which has its most upstream side formed of a convex curve ZU2 with respect to 10 the flowing direction (direction of the arrow shown in Fig. 10) of the leakage flow in the groove 70. Thus, the fifth embodiment of the invention has a wall surface equivalent to the curve ZU2 instead of the wall surface equivalent to the side ZU of the groove 60 of the sealing 15 portion 31 of the hydro turbine 102 of the fourth embodiment. The shape of the groove 70 in the horizontal cross section may be a substantially triangular shape, a substantially pentagonal shape or the like if the most 20 upstream side has the convex curve ZU2 in the flowing direction (direction of the arrow shown in Fig. 10) of the leakage flow. It is preferable that the curve ZU2 has a curvature radius of not less than the width M of the minute gap 25 between the runner band 15 and the sealing liner 22 so to expand moderately the passage cross-sectional area at the inflow portion of the groove 70. In the horizontal cross section, it is preferable that a length R of a normal line drawn from one end of the 30 curve ZU2 at the back of the groove to the curve ZO is not less than the width M of the minute gap between the runner band 15 and the sealing liner 22. When the length R of the normal line is determined to be not less than the width M, a flow velocity of the leakage flow in the 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 24 passage cross section of the sealing portion 31, where the groove 70 is formed, can be decelerated to about 1/2. When the groove 70 in the horizontal cross section is determined to have a substantially quadrangular shape, the 5 side Z1 adjacent to the curve ZU2 may be formed as a curve which becomes concentric with the curve ZO. By configuring in this way, when the leakage flow flows along the curve which becomes concentric with curve ZO, the passage cross section of the sealing portion 31 becomes 10 constant, and the leakage flow is suppressed from separating from the wall surface equivalent to the curve. The loss of the leakage flow due to the friction with the wall surface in the groove 70 can be increased. As described above, since the passage cross-sectional 15 area expands moderately at the inflow portion of the groove 70, according to the hydro turbine 103 of the fifth embodiment, the leakage flow does not separate from the wall surface equivalent to the curve ZU2 but expands while being decelerated along the wall surface. Part of the 20 leakage flow having flowed into the groove 70 suffers loss due to collision, friction with the wall surface and the like. Thus, the sealing effect can be enhanced by increasing the loss in the sealing portion 31 by the hydro turbine 103 of the fifth embodiment. Therefore, the flow 25 rate of the leakage flow can be decreased, and the volumetric efficiency of the hydro turbine 103 can be improved. In the above example, the groove 70 is provided on the surface 24 of the sealing liner 22 which is a 30 stationary portion, but the groove 70 may be formed on the surface of the runner band 15 which is a rotating portion configuring the sealing portion 31. In the above example here, the groove 70 is configured to have a continuous groove structure along the direction of the rotating 35 shaft, but the groove 70 may be provided intermittently 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 25 along the direction of the rotating shaft, namely, a plurality of grooves 70 may be provided with prescribed intervals along the direction of the rotating shaft. In the above examples, the same action and effect as those 5 described above can also be obtained. Evaluation of loss It is described below that the loss can be increased by forming the groove having the above-described predetermined shape on the wall surface of the passage 10 configuring the sealing portion 31. To evaluate the loss, the sealing portion 31 (see Fig. 3) (specification 1) having the groove 40, the sealing portion (specification 2) having a conventional groove and the sealing portion (specification 3) not 15 having a groove provided to the hydro turbine 10 of the first embodiment were subject to numerical analysis of flow to determine losses. Fig. 11 is a view showing in a magnified fashion a meridional cross section of a groove portion of a sealing 20 portion having a conventional groove. In the conventional sealing portion shown in Fig. 11, a horizontal annular groove 80 is formed circumferentially on the surface 24 of the sealing liner 22 configuring the sealing portion 31. The groove 80 is formed into a rectangle (rectangular 25 shape) in a meridional cross section to be perpendicular to the forming direction of the groove 80. Since the specification 3 does not have a groove, the sealing portion is configured of an annular minute gap which is formed between the runner band 15 and the sealing liner 30 22. It was determined that the embodiments tested, referred to in Figure 12 as specifications 1 to 3, have the same structure except that the groove portions only are differently configured. The numerical analysis was performed on the flows of each variant. 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 26 Fig. 12 is a chart showing losses determined by numerical analysis of different flows. It is seen from Fig. 12 that the loss in the specification 1 according to the first embodiment is larger than those in the 5 specification 2 and the specification 3 examples. It is not shown but the sealing portions of the other embodiments of the invention were subject to the same numerical analysis of flows as above to evaluate the losses. It was found that the losses were larger than 10 those in the specification 2 and the specification 3. Evaluation of flow The condition of a flow in the groove of the sealing portion according to the present embodiment was examined. For a comparative baseline, the condition of a flow in the 15 groove of the sealing portion of a conventional hydro turbine was examined. The conditions of flows were determined by the numerical analysis of the flows under steady operating conditions of the hydro turbines. As the groove of the sealing portion according to the 20 present embodiment, the groove 40 shown in Fig. 3 was determined as a basic shape, the shape of the groove 40 in the meridional cross section was determined to be a quadrangular shape, and the side W1 adjacent to the side WU was determined to be parallel to the side WO. The 25 angle 0 formed between the side WU and the side WO was determined to be 300, and the angle a formed between the side WD and the side WO was determined to be 900. Meanwhile, the shape of the groove 40 in the meridional cross section in the sealing portion of the conventional 30 hydro turbine was determined to be rectangular. Fig. 13 is a view showing the condition of a flow in a groove portion of the sealing portion of the embodiment. Fig. 14 is a view showing the condition of a flow in the groove portion of a sealing portion of a conventional 35 hydro turbine. The above results show two components of 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 27 velocity vectors excluding the velocity component in a circumferential direction among the velocity components in a cylindrical coordinate system. As shown in Fig. 13, the groove in the sealing 5 portion according to the embodiment, part of the leakage flow expands along the wall surface in the groove while decelerating the velocity gradually. It is also seen that the flow is narrowed down to become a contracted flow at a region over the groove, namely at a portion where the 10 leakage flow flowing through the sealing portion and the leakage flow from the groove interior join together. Meanwhile, it is seen as shown in Fig. 14 that the leakage flow does not substantially enter into the groove in the sealing portion of the conventional hydro turbine, 15 and vortex flows having a slow velocity are formed in the groove by a shear force due to the leakage flow flowing through the sealing portion. 20 Evaluation of discharge factor of leakage flow A discharge factor of the leakage flow in the sealing portion according to the embodiment was evaluated. For comparative purposes, the discharge factor of the leakage flow in the sealing portion of the conventional hydro 25 turbine was also evaluated. Fig. 15 is a view showing in a magnified fashion a meridional cross section of a sealing portion according to the embodiment. Fig. 16 is a view showing in a magnified fashion a meridional cross section of a sealing portion of 30 a conventional hydro turbine. As shown in Fig. 15, the groove having the shape used for evaluation of the flow described above was formed in a 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 28 plurality of stages (19 stages) in the direction of the rotating shaft in the sealing portion according to the embodiment. As shown in Fig. 16, it was determined that the sealing portion of the conventional hydro turbine was 5 configured to have a three-staged seal structure portion. Fig. 17 is a graph showing the results of measuring the respective discharge factors of the leakage flows of various embodiments of the invention as compared to conventional hydro turbines. The horizontal axis 10 indicates a speed factor nED (1.3.3.12, IEC 60193-1999), which is defined by the following equation (1). The vertical axis indicates a discharge factor QED (1.3.3.12, IEC 60193-1999) of the leakage flow, which is defined by the following equation (2). 15 nED nxD/Eo.5 ... Equation (1) QED=Q/ (D 2xEo 5) ... Equation (2) In the above equations, D denotes an outlet diameter of the runner, which is determined as an outer diameter of the rotating portion as its representative dimension, n 20 denotes a rotational speed of the rotating portion, Q denotes a volumetric flow rate of the leakage flow, and E denotes specific hydraulic energy which is hydraulic energy per unit mass of the leakage flow. The E is defined by the following equation (3). 25 E=gxH... Equation (3) Here, g denotes gravitational acceleration, and H denotes a net head. It was found as shown in Fig. 13 that according to the sealing method of the conventional hydro turbine, the 30 discharge factor of the leakage flow decreases with an increase in speed factor, but the discharge factor of the leakage flow according to the present embodiment does not change substantially. It was also found that according to 4920497 _1 (GHMatters) P87783.AU.1 19/12/13 - 29 the present embodiment, the discharge factor of the leakage flow is small, and the flow rate of the leakage flow reduces in comparison with the sealing method of the conventional hydro turbines tested. 5 According to the above-described embodiments, the loss in the sealing portion is large, so that the sealing effect is high, the flow rate of the leakage flow can be reduced, and the volumetric efficiency of the hydro turbine is at least partially improved. 10 While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various 15 omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and 20 spirit of the inventions. In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or 25 "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments. It is to be understood that, if any prior art 30 publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country. 4920497 _1 (GHMatters) P87783.AU.1 19/12/13