JPS58102130A - Measuring instrument for drag coefficient of riser - Google Patents

Abstract

PURPOSE:To eliminate influences of waves on the water surface, a protection plate against waves and an eddy generating at the end of a test sample by a construction wherein two load cells spaced with a given distance are attached to the portion of the test sample simulated to a riser which is immersed in water. CONSTITUTION:A test sample 19 is attached via a load cell 16 to a piston rod 15 of a hydraulic sylinder 17 set on a carriage. The test sample 19 is provided with a protection plate 20 against waves at its uper part and with two load cells 21, 22 at its intermediate part. With the carriage being stopped or traveled at a constant speed, the cylinder 17 is operated to cause the mounted test sample 19 to vibrate in the direction of arrow. An exciting force exerted on the test sample 19 is detected by the load cell 16 and moments Mx1, Mx2, My1, My2 are detected by the load cells 21, 22, and the detected signals are applied to a data recorder 35 via a dynamic strain gauge 36, thereby to obtain the drag coefficient. In this way, since the drag coefficient is calculated from the sum and difference of those moments, the influence caused by an eddy can be eliminated substantially.

Description

[Detailed Description of the Invention] [Detailed Description of the Invention] [Detailed Description of the Invention] The present invention is based on the drag coefficient #l3iI! which is the dimensionless force of the seagull body force that the riser receives when the riser of Lien) or Marine Live◆ moves slightly in the flow. Ik to do
In particular, by setting i to a value so small that it is completely unaffected by water's surface waves and negligible from the influence of the shaft end of the specimen, and by verifying the actual measurement data at Shimano, it is extremely easy to use. The present invention relates to a drag coefficient measuring device for a lie which can obtain a high degree of loading.

During the installation/reentry work, the installation/reentry (hereinafter referred to as S riser) was carried out from the supporting vessel to the
With the thruster attached to the lower end of the S riser,
Position and control the S riser. At this time, S
1 ml of water rises depends on the physical force (in this case, fluid resistance force) of seawater. In order to do this, it is necessary to calculate this body strength in klm.In addition, when controlling the lower end of the S$1+1 riser to the desired position using a thruster, the thrust;*tm1kat1! There is a fee that is determined in accordance with the vibration and force of the force, and if the flow of fluid force is slow, the position and control will be normal due to the effect of the sea bream I11 thread, mechanical system, and fluid system. It does not work properly and has an unstable aJ luster.

Generally, when a cylinder placed in a hydrostatic fluid vibrates, the fluid force is calculated by integrating the frequently used expression of the cylinder's fluid resistance. However, in the ocean conditions where 11211 reentry work is carried out, the influence of tidal currents and the influence of the rising cedar on the riser are expected to be outside the range of applicable conditions for this calculation formula. It is dangerous to determine C.

For the sake of my enemy, I sent the specimen (1) with a riser as shown in 1st w1J through water II (3
1. A &: M is lowered, the vehicle force or moment applied to the specimen (moving υ in water! 14, therefore p-docel 12) is calculated, and the body force in the two-dimensional plane of the X-Y direction is calculated. The drag coefficient is calculated by making it dimensionless.

1. Apology In this case, firstly, the load cell 12+ is exposed to water, so it is greatly affected by the mm liquid of water.
, 82, since the end direction (4) of the specimen (1) is flat, vortices are generated at the end of the shaft, and the influence of three-dimensional external forces due to these cannot be ignored. Furthermore, the specimen (1
) is installed horizontally on the water surface in order to prevent the wooden surface from rippling once and to minimize the influence of surface waves. Water resistance is also a key factor in measurement differences. These errors I
! ! Regarding the second point (1), the generation of mft1llQ can be minimized by minimizing the distance between the end face 4) of the specimen and the bottom face (6) and 9 of the water (3). Shore 51 In order to do this, depending on the length of the specimen, a large/huge swimsuit is required, and its depth must be kept constant with high precision. It needs to be smooth, which is uneconomical.

The purpose of this project is to improve the above-mentioned measuring device and provide a highly accurate and economical device. , give &111 to the specimen, measure the fluid force of the water applied to the specimen, and calculate the drag coefficient from this fluid force.Measure the drag coefficient of the riser. It is a force that provides a constant load with a live drag coefficient at the point where two rods are brazed with constant inspection on the part immersed in the water.

・An example embodying the present invention will be explained with reference to the attached figures following Figure 112.
m is the drag coefficient-fist** mm according to an embodiment of the present invention
Figures 3 and 4 are diagrams of the working direction of the specimen used in the WTS theory, respectively. # of physical strength calculation formula
It is a schematic-vIi diagram of the specimen used for Q proboscis.

At 112-, on the pedestal (to) are two guide bars (2) parallel to channels all and all of the pedestal, -
- is slowing down. The mounting block supported by the guide bar t1'a so as to be freely movable in the direction of the arrow has a piston rod parallel to the guide bar 1 with a length iL. The screw rod has a p-cell near the tip and a hydraulic cylinder O.
This is the operating axis of B, and the hydraulic cylinder surface is fixed around the base 6. It is desirable to interpose a pair of rollers, etc., in the moving parts between the guide bar 1 (2), the attachment, and the sand plow trowel to obtain smooth tank movement.

j, 1jli lower axis is block or vertical axis (to) -
At the port, the riser was changed and a clam column-shaped test specimen was attached to the lower end of this vertical axis. The hook is a wave-shielding plate attached to the top of the specimen, and two load cells and a spade are installed inside the specimen. IIW
A is (Ill), and the distance from the lower load cell to the end (to) of the specimen (2) is (e2). The wood end of the specimen was machined into a spherical shape in order to avoid the occurrence of roughness in this area. - represents the specimen υ field on the straight axis (
This is a 7-lunge for attaching to (to).

Also, - and (to) are abbreviations for potentiometers for detecting displacement and acceleration of the specimen! Position and J]g?
It is an IM degree needle.

The wjP details of specimen a- are as shown in Figures 3 and 4, and the 1-choice and lower-stage load cells are the same, the threshold of @1, the cylindrical body covered with 1- and the lower part of the lower membrane load 7 11 to defeat
The main body (2) has a hemispherical shape attached to the tip of the cylindrical body (2), and the upper stage load cell is attached to the cylindrical body (2) provided at the threshold of the 7 lunge. It has a shape that resembles a riser. Figure 3 shows a small specimen with a small outer diameter of the load cell movement (to), cylinder (to), ball, -, and the one shown in Figure 4 is specimen a. The outside diameter of the hot water is larger than the load cell, imitating a large riser.

Therefore, the load cell 1 (2) is housed in a cylindrical body provided with a disc-shaped lift (end) and a (turn), respectively. The slit (2) allows the cylindrical body to easily bend in order to increase the sensitivity of the load cell.

Next, parents are taught how to measure using this device.
2. Receive the signals from the device and hydraulic cylinder (2) shown in Figure 2, each load cell, and the progress indicator -1.
The arithmetic unit (Juzu Kyou) that calculates the drag coefficient il'm by y is all moved on the water surface by a script that runs along the water tank. The specimen (2) is immersed in water from the wave shield & (2). There are two titration modes: when the trolley is not running (a constant mode when there is no current) and when the trolley is running (a constant mode when there is a riser in the I4J-Ia flow). There is, a
The S mode is the case where the direction of movement of the Shuchin Lai V- is the same as the running direction of the bogie, and the case where it is made perpendicular to the running direction of the bogie (i.e., when the direction of movement of the tidal current is the same as the running direction of the bogie (i.e., when the direction of movement is at right angles to the tidal current, or approximately at right angles). (When adding fat in the direction) In this way, while the trolley is stopped or running at a constant speed, the hydraulic cylinder tl force is activated, and the mounting is carried out on the block (b) and the specimen ll.
Move the field in the direction of arrow 0 and move Kaede no Gaya.
The wave number is 11IIJ and each data is collected.

The flow of information from each detection is as shown in the #Is diagram,
The position of the sample U hot water is fixed by a potentiometer (2) attached to a hydraulic cylinder, and the DC amplification m@
and then sent to the data recorder. The acceleration of specimen a- was also measured by an accelerometer (to), and 1ILrI
L increase - Sends to the data recorder (to). The 1ilIIR force applied to the specimen is detected by a load cell installed in the middle of the piston rod, and the
) and detected by the upper and lower load cells (-), the specimen is moved in two horizontal directions (
, Y direction) moment) Mx, My 1. MXz
, MFI signals are also sent to the movement meter (to) and can be input to the data recorder. Each data stored in the data recorder can be viewed with a visual graph and a synchronoscope. The filter to be used for this # is a dual-di "hood filter that filters in the same phase because the 7-men F side signal from the load cell must be output with no phase shift. - is a real-time analyzer that performs frequency analysis etc. in real time.

The moment 42 at each load cell that has passed through the dual decade filter (to) is calculated using the following LTT formula: drag + ik number. That is, −
As shown in Figure 6, if the vibration force in the two-dimensional space (due to water) is W, then each load cell (2), (2) Qlj
The moment force acting on -2 is expressed by the following α) formula.

M −L w (h +lz)” ・・・・(I
)-2 town=1. ．． From X, -(7) (I) → billion), we therefore obtain.

By substituting the (conversion) formula into '-2(V雫-雛f-/I,''------η), Ml and M2 are actually measured and 10 is known, so W can be found.

On the other hand, the total resistance force F acting on one part of the specimen is F =
wDJl −:k Cdpv2DJ1−−−−−
(V). Here, D is the outer diameter of the specimen,
is tr1116. 6FI type Nibite ddpiilNI
Since J, V Ha%, flAaiq, /IfI11'' can be obtained by the bone equation, the force coefficient Cd is calculated from the above equation. By substituting the known value of 10, the calculated value of M can be found, or by comparing this value with the actual value of 1g, the validity of the calculated values of Ml and M can be verified. It is a sophistry,
By performing this verification, the greenhouse data 6m-characteristics can be significantly increased and the measurement accuracy can be improved.

Furthermore, Ml and Ml moved to the back are the sum of Ml (moment due to fluid force) and moment M' caused by the vortex straightness generated at one end (end), but in the set, -1 Since the difference between the city and the town becomes an interlayer, the influence of the three-dimensional current force that is the disturbance on one end is almost eliminated, and the detection becomes even more difficult.

1. Rikiji - In the moment, the road is seeking a moment.''
1#/'M was used, but a similar effect was also found by using a four-docel cell that exudes a force of 1=-h applied to the specimen instead. In addition, the shape of the specimen is only cylindrical.
You can choose from 1 square prism and other noodle-shaped items. Further, in the above embodiments, the specimen was moved within the water tank, but the specimen may be fixed and the water allowed to flow.

As described above, in the present invention, two load cells are attached at a certain interval to the submerged part of the specimen, so that three-dimensional disturbances on the wooden surface and the influence of waves can be avoided. Since the load cell does not detect the movement of the wrinkle guard and the difference in the moment acting on the two load cells, the influence of the first force on the axis *S of the specimen is almost eliminated. By doing so, the composition accuracy is dramatically the same, and since a special aquarium with high precision is not recommended, it is a slow fishing, and also by taking advantage of the wave prevention method, the water-low F 1.
A drop of 11 degrees can be eliminated.

1. Since the verification of the data carried out in 1.1 is effective, the 4S chain property of the stagnant shoulder improves considerably. Furthermore, when the wood end of the shaft body is fired into a spherical shape, the occurrence of #& flow at one end is further reduced, improving measurement accuracy, and reducing the output circuit from each load cell. If a dual-decade filter is applied to each of the two, the phases of the outputs from each one-door cell will match, and the difference due to the phase difference will be eliminated.

[Brief explanation of the drawing]

FIG. 1 shows -I! of a conventional measuring device. LI diagram, number 24,
A perspective view of the drag coefficient measuring device according to the present invention - 1 dollar
1311! ! 2. Figure 114 is the same proposal - Individual cross-sectional view of the specimen used in the example, Port 5 Figure 4, - Measurement of the unprecedented example - Block diagram of sweetfish, No. 611, Calculation formula for fluid force. lI! - Approximately the axis-to-center area of the specimen used. J14100m light) 19...Specimen, 21,22...Load cell 23...end@fl,, 39-...Dufulde 4'r-to °filter〇Patent applicant Industrial Technology IIk Director 111-?
, -Figure 3 114 Figure I511

Claims (1)

[Claims] l. Inserting a specimen lying on a riser into water, applying vibration to the specimen to realize the fluid force of water acting on the specimen;
In the riser drag false enemy constant device that calculates the drag coefficient from this m physical strength, the riser drag is characterized by attaching two load cells at a constant value to the submerged part of the test sample. Coefficient measuring device. 2. A live drag-retaining intermittent sardine determination device in which the test specimen has a spherical shape. 3.2 A live drag line constant device according to claim 11JI11m, in which a dual decade 71# tar is provided in one path that receives the signal of @.