LT6091B - Detection method of hydrodynamic characteristics - Google Patents

Abstract

The invention relates to the field of measurement and testing, specifically testing the hydrodynamic characteristics. The invention can be widely applied to hydraulic engineering, shipbuilding, hydropower, designing the bridge supports, breakwaters, berths, water, road signs, water flow energy suppression equipment, ships and submarines elements of other devices that interoperation forces with the current to be evaluated. Detection method of hydrodynamic characteristics at the research in open field conditions in the water, characterized in that a stabilizer (2) is attached to a device (1), hangs with rope (3), submerges in not flowing water, measures the rope force, which pulls a rope, moves to the water flow, again measures the rope drawing power, flow rate, and the rope (3) unbend angle from the vertical position, and then by the measured parameters calculates hydrodynamic resistance and lift forces and factors, and stabilizer (2) for stabilizing the position of testing device is composed of two thin, light, perpendicular to one other plates, joined together and connected to the test device, and stem.

Description

The invention relates to the field of measurement and testing, in particular to the testing of hydrodynamic characteristics. The invention can be widely applied in hydraulic engineering, shipbuilding, hydropower engineering, design of bridge supports, jetties, embankments, waterway signs, water flow energy suppression devices, marine submersibles and other devices whose interaction with flow forces need to be evaluated.

State of the art

There is a known method for determining hydrodynamic forces from pressure measured at several points on the surface of a device moving or circulating in a fluid stream, which channels the control points of the surface of the test device with pressure sensors (see Valter R. Debler, Fluid Machanics, published by Prentice-Hall, Ine. Fundamentals, 1990, pp. 431-441).

The disadvantage of this method is that it requires a hydraulic spout to be fitted, as well as pressure and velocity measuring devices that only specialized laboratories may have. Larger units need to be modeled for exploration because gutters have limited cross-sectional dimensions and water flow rates. Model test results need to be recalculated, and modeling corrections reduce the reliability of test results. The method described is cumbersome, slow and expensive.

A known method for investigating the hydrodynamic pressure forces acting on a high-speed boat hull at various speeds, whereby sensors measure pressure at various points on the boat hull, and calculate resistance and lift forces therefrom. By changing the shape or construction of the underwater or submersible wings or the hull and repeating the research, it looks for the optimal solution (see US 7543544, 06.09.2009).

This method of investigating hydrodynamic pressure forces uses quite sophisticated pressure and velocity measuring equipment, complicated force calculations. The reliability of the results raises serious doubts. Connecting the hardware will damage the boat's hull and will require considerable time and cost to replace and modify, and will cause noisy research, acoustic pollution, and environmentally harmful emissions.

The closest analogue adopted by us as a prototype is a method of studying the hydrodynamic resistance of marine fishing nets. This grid model is tested on a large (21.3x8.0x2.7 m) hydraulic duct, where pumps create water flow, measure water velocity with hydrometric spinners, measure forces with dynamometers, and examine the shape of the grid using photographic techniques (see PF Lader and B. Enerhaug's article, "Experimental Investigations in Forces and Geometry of a Net Cage in Uniform Flow," published in Journal of Oceanic Engineering, 301, No. 1, pp. 79-84, 01.01.2005.

Unique and sophisticated laboratory equipment limits the use of this technique. In addition, this method is complex, expensive and slow.

The essence of the invention

AIM OF THE INVENTION: To provide a simple, inexpensive, and fast way to investigate hydrodynamic forces in a fluid-moving or fluid-flow device under field conditions without modeling or damaging it.

The object of the invention is achieved by the fact that in the method of determining hydrodynamic characteristics, the device is fitted with a stabilizer, suspended by a rope, submerged in the water, measured by the tensile force, transferred to the water flow, the flow velocity and the angle of inclination of the rope from the vertical position, then calculates the hydrodynamic drag and lift forces and their coefficients from the measured parameters, and the stabilizer for the required position of the test piece consists of two thin, perpendicular plates connected to each other device, and mast.

Brief description of the drawings

The invention is illustrated in Figure 1, which is a schematic diagram of equipment for testing hydrodynamic forces on a device under water flow.

The equipment consists of a test device 1 with a stabilizer 2, a rope 3 for hanging an object, a dynamometer 4, a crane 5, which is placed on a bridge 6. The object is lowered to the river flow as close to the water surface 7 and further to the river bottom 8. uses a float 9 or a hydrometer spinner (not shown in the diagram). The inclination angle a of the rope 3 is measured, the reading of the dynamometer 4 is counted, and the movement of the float 9 is monitored by a theodolite on the river bank (not shown) The time t during which the float 9 flushes / measures the second.

Implementation of the invention

The effects of flow on the device are investigated as follows.

A stabilizer 2 is mounted on the device 1 to maintain the flow in the required position in the required position. The unit is then connected to a dynamometer 4 with a rope 3 not exceeding 1.0 m long, which is connected to the crane hook 5 as long as possible (see Fig. 1). The device 1 is submerged in still water, for example at the bridge support, downstream thereof, and submits the reading Fi of the dynamometer 4. Subsequently, the device 1 displaces the flow of the river j, subtracts the reading F2 of the dynamometer 4, measures the angle a of the rope 3 from its vertical position. Throws float 9 from the bridge into the river and measures the time t by which float 9 flies the distance /. The hydrodynamic resistance force exerted by the flow at v = llt is calculated by the following formula

F _D = F ₂ * sina, (1) o lifting force F _l = F ₂ * cos a. (2)

The hydrodynamic drag coefficient is calculated by the formula C „= 2F _D / (fiA _x v ² ), (3) and the hydrodynamic lift coefficient ą = 2ą / (^ _; v ^! ). (4)

Here, A _x and A _z are the projection areas of the projected object into the flow cross section and j horizontal plane, respectively.

Industrial applicability

Compared to the prototype, the new method for determining hydrodynamic characteristics is simple, fast, inexpensive and easy to use in outdoor conditions using conventional construction practices. The test objects are of unlimited dimensions, so there is no need to produce models whose test results have to be recalculated in practice by introducing inevitable scaling errors.

The method is used in field conditions, the study is conducted in a river, so the device or design itself is tested and there is no need to produce a model of the device which simplifies, speeds up and lowers the cost of the study. It can be tested even at low river flow rates (<0.5 m / s), when the hydrodynamic forces acting on them are small and difficult to measure accurately in conventional ways. The investigation shall not cause any damage to the site or any environmental impact.

Claims (2)

Definition of the Invention 1. Method for the determination of hydrodynamic characteristics in a field test in an open water body, characterized by attaching a stabilizer to the test facility, hanging it on a rope, submerging it in tension, transferring it to the water flow, re-measuring the tensile strength of the rope. , flow velocity and angle of incline of the rope, then calculate the hydrodynamic drag and lift forces and their coefficients from the measured parameters. Method for the determination of hydrodynamic characteristics according to claim 1, characterized in that a stabilizer consisting of two thin, light, perpendicular plates connected to each other and connected to the test device is provided for maintaining the required position of the device under test.