Background technology
Deep water top tension type vertical pipe is a kind of main Types of deep water marine riser, and the lower end of standpipe is connected with subsea wellheads, and wall tension acts directly on the well head, and the fluid in the pipe passes standpipe from the seabed continuously and flows to floating platform.The bending stiffness of deep water top tension type vertical pipe comprises the geometric stiffness that resistance stiffness and tension force cause, wherein geometric stiffness is based on that the complicated bend of beam is theoretical to be calculated.And the complicated bend theory of beam is to be based upon on the basis of solid beam Analysis on Mechanics Model, and its tension force born by the cross section fibres of beam fully.But standpipe is hollow, and inside is full of liquid, and liquid can not be born any tension force, and shape changes with container shapes.Therefore, the solid fiber effect of the effect of liquid and solid beam is diverse.Liquid not only can not bear the axial tensile force of standpipe, and can not form to tube wall constraint and the squeezing action of any solid fiber.Therefore, the geometric stiffness of standpipe should adopt wall tension to calculate.
But present deep water top tension type vertical pipe geometric stiffness is to adopt the effective tension of standpipe xsect to calculate, and specific formula for calculation is as follows:
In the formula: [K
G] be geometric stiffness matrix;
T
eBe effective tension;
[N] is the unit interpolating function of standpipe;
L is the element length of standpipe.
And effective tension is based on that theoretical formula that law of buoyancy and equilibrium condition derive calculates, as shown in the formula:
T
e=T
w-p
iA
i+p
0A
0 (2)
In the formula: T
wBe the standpipe wall tension;
p
i, p
0Be respectively the inside and outside pressure of standpipe, wherein p
iDo not comprise hydrostatic head pressure;
A
i, A
0Be respectively the inside and outside wall cross-sectional area of standpipe.
The unreasonable part of above-mentioned account form is that liquid is treated as solid, thereby causes the unreasonable of existing standpipe geometric stiffness calculating.The geometric stiffness of standpipe should adopt wall tension or effective tension calculates the concern that has been subject to Chinese scholars, and the unique method that addresses this problem is experimental study.At present, still nobody finishes the geometric stiffness experimental study of standpipe.
Summary of the invention
The object of the present invention is to provide a kind of test unit of deep water top tension type vertical pipe geometric stiffness, thereby solve the reasonable computation problem of deep water top tension type vertical pipe geometric stiffness.
Technical scheme of the present invention is as follows: a kind of geometric stiffness test unit of deep water top tension type vertical pipe, comprise the model pipeline that is arranged on the fixed mount, and model pipeline peripheral hardware has water drum, model pipeline upper and lower end and water supply line system connectivity; Top or bottom at fixed mount are provided with reaction frame, and reaction frame is connected with the chuck that is arranged on model pipeline top or bottom by spring, and described spring is provided with the spring tension meter; Post for the wall tension force of measurement model pipeline and the foil gauge of vibratory response at the model pipeline.
Further, the geometric stiffness test unit of aforesaid deep water top tension type vertical pipe, wherein, described water supply line system comprises the source line that is communicated with the upper end of model pipeline and the discharge pipe that is communicated with the lower end of model pipeline, is provided with by-pass line between source line and the discharge pipe; The two ends of source line and discharge pipe are respectively equipped with valve, and the end of discharge pipe is connected with water tank, and water tank is connected with water pump by the water tank outlet.
Further, the geometric stiffness test unit of aforesaid deep water top tension type vertical pipe wherein, is provided with tensimeter at described source line.
Further, the geometric stiffness test unit of aforesaid deep water top tension type vertical pipe wherein, is equipped with chuck in the upper and lower of model pipeline; When reaction frame was arranged on the bottom of fixed mount, the chuck of bottom connected chute by support, and chute is arranged on the slideway of fixed mount, and the chuck on top directly is connected with fixed mount by support; When reaction frame was arranged on the top of fixed mount, the chuck on top connected chute by support, and chute is arranged on the slideway of fixed mount, and the chuck of bottom directly is connected with fixed mount by support.
Further, the geometric stiffness test unit of aforesaid deep water top tension type vertical pipe, wherein, described water drum is fixed on the fixed mount by clip, is full of water in the water drum; The cylinder of model pipeline and water drum seals with glass cement at the end.
Beneficial effect of the present invention is as follows: the present invention can pass through the tensioning spring tautness meter, and the support of chuck is moved down along slideway, and the model pipeline is tensioned, thereby simulation applies tension force; The control of the adjusting implementation model pipeline internal pressure by valve and water pump; By the Disturbance Model pipeline, make it produce free vibration, thereby realize measurement and the checking of various data.The present invention can finish the experimental study of deep water top tension type vertical pipe geometric stiffness, and calculating for the standpipe geometric stiffness provides foundation and verification experimental verification.
Embodiment
Describe the present invention below in conjunction with the drawings and specific embodiments.
As shown in Figure 1, the geometric stiffness test unit of deep water top tension type vertical pipe comprises the model pipeline 1 that is arranged on the fixed mount 13, the model pipeline 1 outer water drum 2, model pipeline 1 upper and lower end and water supply line system connectivity of being provided with.The water supply line system comprises the source line 14 that is communicated with the upper end of model pipeline 1 and the discharge pipe 15 that is communicated with the lower end of model pipeline 1, is provided with by-pass line 16 between source line 14 and the discharge pipe 15.The upper end of model pipeline 1 is connected with the outlet of water pump 18 by source line 14, be provided with tensimeter 29 at described source line 14, the end of discharge pipe 15 is connected with water tank 31, water tank 31 is connected with the entrance of water pump 18 by water tank outlet 17, and described water pump 18 is connected with motor 20 by shaft coupling 19.Valve 22 and valve 26 are equipped with in the two ends of source line 14, so that the pressure of control model pipeline 1; Valve 24,25 is equipped with at the two ends of discharge pipe 15; Also be provided with valve 23 between by-pass line 16 and the source line 14.
Top or bottom at fixed mount 13 are provided with reaction frame 11, and reaction frame 11 is arranged on the bottom of fixed mount 13 in the present embodiment.Reaction frame 11 is provided with reaction frame stiffening rib 12, reaction frame 11 and reaction frame stiffening rib 12 are welded to connect and are weldingly fixed on the fixed mount 13, reaction frame 11 is connected with the chuck 3 that is arranged on model pipeline 1 bottom by spring, and described spring is provided with spring tension meter 28.Post for the wall tension force of measurement model pipeline and the foil gauge 27 of vibratory response at model pipeline 1.
Be equipped with chuck 7 and chuck 3 in the upper and lower of model pipeline 1, the chuck 3 of bottom connects chute 6 by support 4, and chute 6 is arranged on the slideway 10 of fixed mount 13; The chuck 7 on top directly is connected with fixed mount 13 by support 8.Be welded with support reinforcement 5 on the support 4, be welded with support reinforcement 9 on the support 8.Those skilled in the art will appreciate that when reaction frame is arranged on fixed mount top the support of the chuck 7 on top should fill chute, slideway also should be arranged on top, and chuck 3 then no longer needs chute, and should fix, and namely the set-up mode of chuck 3 and chuck 7 exchanges.
Described water drum 2 is fixed on the fixed mount 13 by clip 30, is full of water in the water drum 2; The cylinder of model pipeline 1 and water drum 2 seals with glass cement at the end.
The method that the geometric stiffness that adopts said apparatus to carry out deep water top tension type vertical pipe is tested is as follows:
(1) water tank 31 water-fillings
Water tank 31 is filled with water under the source line 15, and water drum 2 is water-filling not.
(2) to model pipeline 1 water-filling
Open valve 21,22,26,25 and 24, valve-off 23 starts water pump 18.
(3) keep the water of model pipeline 1 not flow
After the source line 15 normal water outlets of water tank 31, valve-off 25 and 26 switches off the pump 18, and keeping the hydraulic pressure in the model pipeline 1 is hydrostatic head pressure, at this moment, foil gauge 27 answer vanishing, namely the interior pressure of model pipeline 1 does not cause wall tension.
(4) model pipeline 1 is applied tension force
Tensioning spring tautness meter 28 makes the support 4 of chuck 3 move down along slideway 10, and model pipeline 1 is tensioned.From the readable strain that goes out model pipeline 1 of foil gauge 27, answer allergic effect between 500~1500.Because the hydrostatic head pressure in the model pipeline 1 does not produce axial strain, therefore, the reading of foil gauge 27 all is that tension force causes, then the effective tension in cross section equals wall tension at this moment:
T
e=T
w
(5) free vibration test
The reading of record spring tension meter 28 and foil gauge 27, then the Disturbance Model pipeline 1, makes it produce free vibration, records foil gauge 27 time dependent data (strain time-histories).
(6) calculation on Natural Frequency
The strain time-histories is made analysis of spectrum, such as Fast Fourier Transform (FFT), the natural frequency f of the model pipeline 1 when obtaining effective tension and equaling wall tension
1
(7) tension force of removal model pipeline 1
Retracting spring tautness meter 28 makes the strain of model pipeline 1 be decreased to zero.
(8) water pressure in the increase model pipeline 1
Valve-off 22 and 24, Open valve 23 and 25, unclamp chuck 3, open water pump 18, the strain that applies the tension force generation in reading that water pressure in the model pipeline 1 increases to foil gauge 27 and the step (4) is equated, be that wall tension force equates with the wall tension force of step 4, valve-off 23,25 and water pump 18 is tightened chuck 3.
The wall tension force of this moment is:
T
w=p
iA
i
Therefore, effective tension is:
T
e=T
w-p
iA
i=0。
(9) free vibration test
Disturbance Model pipeline 1 makes it produce free vibration, records foil gauge 27 time dependent data (strain time-histories).
(10) repeating step (6) is obtained the null model pipeline 1 natural frequency f of effective tension
2
(11) compare f
1And f
2, can draw the natural frequency that does not have different effective tensions under the external pressure condition.If f
1=f
2, then geometric stiffness is calculated and should be adopted wall tension force, otherwise, should adopt effective tension computational geometry rigidity.
(12) water drum 2 water-fillings
The water-filling degree of depth of water drum 2 is answered so that the external pressure of foil gauge 27 height satisfies following formula:
p
0A
0≠T
w
The effective tension of this moment:
T
e=p
0A
0
(13) free vibration test
Disturbance Model pipeline 1 makes it produce free vibration, records foil gauge 27 time dependent data (strain time-histories).
(14) repeating step (6) is obtained effective tension T
e=p
0A
0The time model pipeline 1 natural frequency f
3
(15) the interior pressure of removal model pipeline 1
Unclamp chuck 3, Open valve 22,24,25 and 26, valve-off 23 is opened water pump 18, and the interior pressure of removal model pipeline 1 so that the reading of foil gauge 27 is down to zero, is tightened chuck 3.
(16) model pipeline 1 is applied tension force
Tensioning spring tautness meter 28 makes the support 4 of chuck 3 move down along slideway 10, and model pipeline 1 is tensioned.The standard of tensioning is that the reading of foil gauge 27 equates with step 8 or step 4.Because the hydrostatic head pressure in the model pipeline 1 does not produce axial strain, therefore, the reading of foil gauge 27 all is that tension force causes, then the cross section effective tension of this moment is:
T
e=T
w+p
0A
0
A) repeating step (13).
B) repeating step (6) is obtained effective tension T
e=T
w+ p
0A
0The time model pipeline 1 natural frequency f
4
Compare f
3And f
4, can draw the natural frequency of different effective tensions under the external pressure condition.If f
3=f
4, then geometric stiffness is calculated and should be adopted wall tension force, otherwise, should adopt effective tension computational geometry rigidity.
Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technology thereof, then the present invention also is intended to comprise these changes and modification interior.