# Method of determining hydraulic friction loss

FIELD: agriculture.

SUBSTANCE: method comprises modeling the process of interaction of water flow with a rough surface by changing the working member of the sloping chute for a precision member with the smooth surface, measuring the height of the water flow in the entrance and exit sections of the chute by means of micrometer with measuring needle, determining the flow rate, and measuring the width of the chute. The smooth member is changed for the working member provided with a rough surface, and the height of the water in the exit section of the chute is measured.

EFFECT: simplified method.

4 dwg

The invention relates to agriculture, in particular to methods for the study of the flow of melt and rain waters arising on stationery surface (on the slopes, gully network in temporary streams and so on), and can be used in the field of hydrology, hydraulic engineering, reclamation, industrial, civil and road construction.

There is a method of determining the hydraulic friction losses, including the depth measurement of fluid flow by means of testera [2, s]with Vernier with a multiplier of 0.1 mm, and the liquid flow through the Weir Thomson [2, p.123].

Evaluation of hydraulic friction losses produced by the hydraulic resistance coefficient [2, s], which is determined using formula A. Darcy - Uwabaki

where λRthe hydraulic resistance coefficient; g - acceleration of gravity; R is the hydraulic radius; i - slope; V - velocity of water flow.

When designing hydraulic structures are usually encountered with quadratic resistance area, when the water flow has enough speed where you can apply the Chezy formula [4, s], using estimates of hydraulic friction loss coefficient Chezy

where C is the Chezy coefficient; V is the velocity of the Otok water; R is the hydraulic radius; i is the gradient of the slope.

To calculate the above ratios With and λRrecommended roughness coefficient n, proposed by Swiss engineers Eganville and Cattenom, the definition of which is possible on the table Langille-Cutter [4, s].

The disadvantage of this method is that when determining the parameters of fluid flow (flow rate, the height of the thread) it is necessary to establish uniform motion [2, s]; the use of empirical and semi-empirical formulae for determination of hydraulic resistance coefficient λRand Chezy coefficient C, the use of which is limited by the limits of the experiments on which they are based [2, p.123]; the use of the roughness coefficient n in table Langille-Cutter on the basis of purely descriptive (rather than quantitative) characteristics of the channel [4, s]; the coefficient of hydraulic resistance λRand the Chezy coefficient With values are not constant and depend on different parameters of stream and river channels [1, p.33].

The purpose of the invention is to simplify the method for determining the hydraulic friction losses.

This objective is achieved in that in the method of determining the hydraulic friction losses, including the modeling of the interaction process water stream with a rough surface, for which sportsouth the working part of the inclined trough, made in the form of precision fabricated sample with smooth and rough surface, measure the height of the water stream using a micrometer with gauge needle in the input and output parts of the tray, determine the water flow rate, measure the width of the tray, and the dimensionless figure ϕby which assess the hydraulic friction losses, is determined by the formula

where QIn- water consumption, m3/s; hg- the height of the water flow in the output of the tray when interacting with a smooth surface, m; hW- the height of the water flow in the output of the tray when interacting with a rough surface friction, m; hB1- the height of the water flow in the front part of the tray, m; width tray, m; g - gravitational acceleration, m/s2; z is the vertical coordinate between the centers of gravity flow in the cross section of flow in the input and output parts of the tray, M.

For explanation of formula (1) consider the flow of water in the tray with smooth surface friction (figure 1) and with a rough surface friction (figure 2). For one dimensional flow equation of continuity can be written

where Ux- the speed of the water in the tray on X.

Multiplying equation (2) Ω dx and integrating, we obtain the consumption of water in the tray

where Qinthe flow in the water in the tray; Ω - screening area flow; V is the average speed in the live section.

Equation (3) shows that at the steady state flow of water in the tray, despite the change in average velocity V and living areas-sections Ω the length of the stream, the flow rate Qinit remains constant.

Change in average speed can be determined from the following assumptions. Let the stream of the screening area d Ω speed on separate lines in the same current. Then the stream per unit of time is the amount of water

In hydrodynamics [4] under the average speed in the live section realise such a speed that should move all fluid particles in the flow to pass through his living section of the actual consumption. Therefore, for clarity, simultaneously with the actual flow consider a dummy stream, which all streams in the live section have the same velocity Ux. For a thread when Ux≡V equation (4) can integrate

Hence the expression to determine the average speed

From equations (3) and (5) we can obtain the dependence of

showing that the average speed is always inversely proportional to the squares of the ratios is ejstvujuschij living sections. So

where is the width of the tray; VinVg- the rate of flow of water respectively at the inlet (section 1-1) and output (section 2-2) parts tray; hinhg- the height of the water flow, respectively, on the input (section 1-1) and output (section 2-2) parts of the tray.

The mass of water flowing through the tray during t:

where ρin- the density of water.

The change in kinetic energy of the water in sections 1-1 and 2-2:

Expression (10) subject to (8) and (9) after some transformations will be copied

The change of total energy in sections 1-1 and 2-2

where z is the vertical coordinate between the centers of gravity flow in sections 1-1 and 2-2.

Consider the flow of water in the tray with a rough surface friction (figure 2).

The energy change of the water in the tray, respectively, in sections 1-1 and 2-2

where VB1VW- the rate of flow of water respectively at the inlet (section 1-1) and output (section 2-2) parts of the tray.

Because here consider the interaction of water flow with unyielding surface friction, there is reason to believe that

where mW, mB1the mass of water, flowing through the tray at time t.

As for the case in question

the expression (13) after some transformations takes the form

The change of total energy in sections 1-1 and 2-2

where z′ - the vertical coordinate between the centers of gravity flow in sections 1-1 and 2-2.

Dividing the expressions (12) and (17) on the gravity of the flowing water mWg=mgg=ρinQintg, obtain the formula for determining the change in the intensity of energy flow:

where agthe change in specific energy of the fluid flow in the interaction with a smooth surface, m; AndWthe change in specific energy of the fluid flow in the interaction with a rough surface friction, m

Experimental studies have shown that hin≈hB1z≈z′ at the same values of Qin.

Let us introduce the dimensionless figure ϕ:

Substituting expressions (18) and (19) (20) subject to hin≈hB1and z≈z′get the formula (1)

Evaluation of hydraulic friction losses based on specific values of the dimensionless figure ϕ may be sudestada as follows. From the expression (20) or (1) the desired value AndWequal to

and the magnitude of the pressure losses along the length on the smooth surface friction is determined by the formula [4, s]

where λgis the coefficient of hydraulic resistance on a smooth surface friction; lg- the length of the smooth friction surface, m; Vg- speed flow over a smooth friction surface, m/s; Rg- hydraulic radius, m In the formula (22) the change in specific energy of the fluid flow Andghas a dimension, expressed in units of length, and is equal in magnitude to the pressure losses along the length of the hl.

Then the expression (21) with (22) takes the form

where hl- the pressure loss along the length on a rough surface friction, m

In this case, to determine the pressure loss along the length on a rough surface friction hl=AWenough to know for hydraulically smooth friction surfaces of tabular data values λg[4, pp.163] and specified values of lgVg, Rg≈hgand the dimensionless figure ϕ.

Figure 3 shows a device for the implementation of the proposed method [3]; figure 4 - section a-a figure 3.

The device consists of an inclined tray 1 is fixed on the base 2 (Fig 3), the de tray is composed of three separate parts, consisting of input and output 3 made with hydraulically smooth surface (e.g. mirror glass), and working 4, made with the investigated rough surface, precision installed between the input and output parts with micrometer screws 5, placed in the base 2, 6 micrometers with measuring needles 7 installed in the input and output parts of the tray along its longitudinal axis on the side walls (figure 4), 8 corners, placed on the sides of the base along the entire length, ensuring the straightness of the tray 1. The device is equipped with a power supply system 9 constant pressure, the damper 10 and the clamp Hoffmann 11.

The method is implemented as follows. Before the beginning of experiments instead of the working part 4 in tray 1 set of precision fabricated sample with a hydraulically smooth surface (e.g. mirror glass), which lines the joint hydroisolyatsia (conventionally not shown). Then with the help of the power system constant head is set to the specified water flow rate QIn. Opens the clip Hoffman 11 and 6 micrometers with measuring needle 7 measured the height of the water flow in the input hB1and the output hgthe parts of the tray 1. The results obtained are recorded in the log of observations.

Then replace the glass in the tray 1 set working frequent the 4 with a rough surface. Junctions of the working part 4 and tray 1 waterproofed. Opens the clip Hoffman 11 and 6 micrometers with measuring needle 7, with the aforementioned method, measured the height of the flow of water (hinin the front part of the tray (as a result of research it was found that for the same set of cost stream height hin≈hB1so hinnot measured) and the height of the flow of water (hWthe output of the tray. The obtained data QInhin≈hB1hghWare substituted in the expression

where QIn- water consumption, m3/s; hg- the height of the water flow in the output of the tray when interacting with a smooth surface, m; hW- the height of the water flow in the output of the tray when interacting with a rough surface friction, m; hB1- the height of the water flow in the front part of the tray, m; width tray, m; g - gravitational acceleration, m/s2; z is the vertical coordinate between the centers of gravity flow in the cross section of flow in the input and output parts of the tray, M.

An example implementation of the method is given in the table. The fraction of particles of a specific average diameter d obtained using the sieve analysis of sand located on ancient alluvial deposits.

Sources of information

1. Grishanin C.V. Hydraulic resistance natural Ruse is/ Kvien. - SPb.: Gidrometeoizdat, 1992. - 180 S.

2. Zegzhda A.P. Hydraulic friction losses in ducts and pipes/ Apegga. - L.-M.: Gastrolyzer, 1957. - 278 S.

3. RF patent № 2021647, class. And 01 In 13/16, 1994.

4. Chugaev P.P. Hydraulics: Textbook for universities/ RPE. - SPb.: Energoizdat, 1982. - 672 S.

1. The method of determining the hydraulic friction losses, including the modeling of the interaction process water stream with a rough surface, the height measurement of fluid flow, characterized in that when carrying out experiments with smooth and rough surfaces using the inclined trough measure the height of the water stream using a micrometer with gauge needle in the input and output parts of the tray, determine the water flow rate, measure the width of the tray, and the dimensionless figure ϕby which assess the hydraulic friction losses, is determined by the formula

where Qin- water consumption, m3/s; hg- the height of the water flow in the output of the tray when interacting with a smooth surface, m; hW- the height of the water flow in the output of the tray when interacting with a rough surface friction, m; hB1- the height of the water flow in the front part of the tray, m; width tray, m; g - gravitational acceleration, m/s2; z - verticalalign between the centers of gravity flow in the cross section of flow in the input and output parts of the tray, m

Same patents:

FIELD: engineering of equipment for friction tests.

SUBSTANCE: as sample holder a shaft is used, which is connected by means of connecting rod mechanism to swinging movement drive, made with possible setting of shaft rotation angle and its rotation speed during rotation for given angle. On top of sample a counter-sample is mounted with its own holder. Sample loading unit abuts by rollers on counter-sample holder. Measuring system includes forces indicator, connected to counter-sample holder, sample movement indicator, connected to its holder, indicator of load output, connected to samples loading unit, optical-mechanical indicators, each one of which is made in form of disk with slits pinned onto axis of arrow of appropriate indicator between emitter and photo-detector, and is connected to computer through mouse port.

EFFECT: increased trustworthiness and precision of tribological characteristics of round and spherical bodies during rotation thereof.

6 cl, 3 dwg

FIELD: test equipment.

SUBSTANCE: machine can be used for testing materials and lubricant matters for complicated trajectories relatively movement of interacting friction pairs. Two-coordinate friction machine has base, sample's holder, two-coordinate drive, counter-body's holder, loading mechanism interacting counter-body, two-component force detector connected with counter-body's holder, program control system and friction force main vector instant value automated estimation system. Two-coordinate drive is made in form of two independent movable carriages which move at mutual-perpendicular directions. Holder of flat sample is disposed onto one carriage and counter-body's holder, loading mechanism interacting with holder and two-component force detector connected with holder of counter-body are disposed on the other carriage. Program control system is made in form of control computer connected with independent control modules and with electric engines through matching unit. Electric engines drive two-coordinated drive into motion to provide movement of indicator which interacts with working surface of sample along continuous nonlinear two-dimensional trajectory.

EFFECT: widened functional abilities; improved precision; better truth of result.

4 cl, 1 dwg

FIELD: investigating or analyzing materials by mechanical methods.

SUBSTANCE: device comprises base, holder for specimen mounted on the base, carriage with holder for counter-body, loading unit, meter of friction force, drive for moving one of the holders, guide secured to the carriage perpendicular to the surface of the specimen, rod that can be set in translational motion in the guide, loading unit mounted at one of the ends of the rod, pivot mounted at the other end of the rod, holder made of a rod whose one end is secured to the axle of the pivot and the other end is provided with counter-body, spring, meter of friction force mounted on the carriage oppositely from both sides of the holder of counter-body and parallel to the plane of the specimen at the same distance from the axis of the pivot to the working surface of the specimen. The spring locks the holder of counter-body perpendicular to the working plane of the specimen. The axis of rocking of the pivot is parallel to the surface of the specimen and perpendicular to the direction of movement of the specimen and counter-body.

EFFECT: expanded functional capabilities.

1 cl, 1 dwg

FIELD: measurement technology; test equipment.

SUBSTANCE: method intends for inspection of rolling bearings, plain bearings and bearing units in instrument engineering, mechanical instrument engineering and electric machine engineering. One ring of bearing is loaded with permanent radial force and the other one is brought into oscillatory motion with specified frequency and amplitude by means of electro-mechanical system made of sync electric motor provided with active rotor and with two windings on stator. One winding is connected with dc source and the other one is connected with ac source. Alternative current is measured in second winding. Angular speed of oscillations of rotor is measured additionally and equivalent dissipative factor is calculated as product of constitutive factor of electric motor and relation of average meaning of current value product during period by speed to average square speed within the period.

EFFECT: improved precision of measurement.

1 dwg

FIELD: investigating or analyzing materials.

SUBSTANCE: method comprises measuring parameters of the pavement and calculating the grip coefficient. First, the ordinate of the micro-profile of pavement is measured, and then the dependence y = f(x), which describes the micro-profile in a given section, is determined. The dependence is used for determining the length of the curve of micro-profile, and parameters Ki of the pavement roughness are determined from the formulae proposed.

EFFECT: simplified method and reduced cost of determining.

2 dwg

FIELD: investigating or analyzing materials.

SUBSTANCE: device comprises housing, mechanism for loading, specimen holders that are provided with parallel bearing planes and mounted one opposite to the other. One of the holders cooperates with the loading mechanism. The mandrel provided with the spherical indenter is interposed between the specimen holders. The device has the mechanism for rotation of the indenter around its axis and unit for measuring the applied moment. The mechanism for rotation of the indenter is made of the lever secured to the mandrel, segment secured to the lever, and flexible link that embraces the segment and undergoes the load.

EFFECT: expanded functional capabilities.

1 dwg

FIELD: investigating or analysis of material.

SUBSTANCE: method comprises determining the limit value of the stress by measuring the angle of inclination of the surface which is provided with the initial material. The device comprises changeable coating with projections and locking member made of a frame having thin baffles or thin film made of an adhesive agent.

EFFECT: improved method.

2 cl, 3 dwg

FIELD: plastic metal working.

SUBSTANCE: method comprises calculating the stress-strain condition of the tool and blank with regard for their materials and geometry, plotting a diagram "deformation force - friction coefficient" of the process of plastic deformation, determining experimentally the deformation force, which corresponds to the actual condition of the surfaces of tool, blank, and lubricant, and determining friction coefficient from the diagram.

EFFECT: enhanced accuracy and reduced labor consumption for determining.

3 dwg

FIELD: measuring engineering.

SUBSTANCE: instrument has platform pivotally connected with the base, box without bottom filled with plastic material, tie-rod device, bearing member which can be adjusted in height with spacers and guides mounted on the plate. The layer of material comprises particles. The box is connected with the platform through a damping link provided with arresting carrier.

EFFECT: enhanced accuracy of measurements.

2 dwg

FIELD: tribometry.

SUBSTANCE: device has the platform which is provided with an article and set on rollers, drive for reciprocating, unit for loading articles, and pickups for recording forces and displacements .

EFFECT: enhanced accuracy of testing.

1 cl, 3 dwg

FIELD: measuring techniques.

SUBSTANCE: method and device can be used for measurement of hydraulic-dynamic resistance of different surfaces moving in fluid. Time of load descending, which load is kinetically connected with disc rotating in water, is compared when surface of load is coated with different matters.

EFFECT: simplicity at use; reduced cost.

2 cl, 1 dwg

FIELD: experimental hydrodynamics.

SUBSTANCE: method comprises making a model dynamically similar to the marine engineering structure in mass, sizes, location of the center of gravity, and inertia moment and mounting the model in the experimental tank by means of anchor-type links provided with dynamometers. The device comprises experimental tank and model provided with anchor-type links for connecting with the frame. The anchor-type links are provided with dynamometers and devices for control of initial tension. The frame has flat horizontal base, vertical pillars , and blocks. The base is provided with the members for securing the vertical pillars at specified points of the base. The vertical pillars are provided with blocks and members that are mounted for permitting movement along the pillars and their locking at a given position. The model is provided with the pickups of angular and linear movements. The outputs of the dynamometers and pickups of angular and linear displacements of the model are connected with the input of the computer.

EFFECT: expanded functional capabilities.

2 cl, 3 dwg

FIELD: aviation industry.

SUBSTANCE: device helps to get real pattern of liquid pressure distribution which flows about "blown-about" object in water tunnel. Device has driven frequency pulse oscillator, frequency divider, control pulse counter, longitudinal contact multiplexer which connect capacitors with shelves, lateral contact multiplexer which connect the other output of capacitors, matching unit, analog-to-digital converter, indication unit, water tunnel, blown-about object, grid with capacitive detector.

EFFECT: improved precision of measurement.

2 dwg

FIELD: physics.

SUBSTANCE: in through portion of pipe with choking of through portion cavitation flow lock mode is set, and in zone of low density value of critical pressure of cavitation and liquid flow are determined, which flow is used to determined liquid speed in pipe neck. Received critical pressure value of cavitation is aligned with pressure of saturated steam of pumped liquid, after that to specially built calculation graph dependencies of relative value of critical pressure of critical speed of flow in channel neck are applied in the moment of setting of lock mode with different concentration of cores target concentration of cores of cavitation of pumped liquid is determined.

EFFECT: higher efficiency.

4 dwg

FIELD: mechanical engineering; testing facilities.

SUBSTANCE: invention can be used for stand tests of pumps of any application. According to proposed method full pressure at pump input is maintained constant by means of reservoir with free surface of liquid exposed to constant (atmospheric) pressure installed in intake pipeline. Working liquid saturated vapor pressure at pump input is changed by heating. Periodical measurement of required parameters in process of liquid heating makes it possible to calculate sought for cavitation margin Δh. Method is implemented by test stand containing pump to be tested, output throttle, flow meter, heat exchanger, service tank, pipe fittings, all arranged in closed hydraulic circuit, and reservoir with free surface of working liquid in combination with capsule made of heat conducting material connected to circuit at pump input. Space of capsule is divided into two parts, one of which is partly filled with working liquid and sealed, and other communicates with circuit.

EFFECT: improved accuracy of measurements and simplified determination of pump cavitation characteristics.

3 cl, 1 dwg

The invention relates to a device for measuring linear displacements of the object, in particular to devices for measuring sediment and trim models floating tools

The invention relates to shipbuilding and relates to a technology for dynamic characteristics of ship traffic at the design stage

The invention relates to shipbuilding and concerns the design of the equipment for pools water tank

The invention relates to experimental hydrodynamics of ship and relates to measuring equipment for testing models of ship propulsion systems in hydrodynamic and ice model basins

FIELD: mechanical engineering; testing facilities.

SUBSTANCE: invention can be used for stand tests of pumps of any application. According to proposed method full pressure at pump input is maintained constant by means of reservoir with free surface of liquid exposed to constant (atmospheric) pressure installed in intake pipeline. Working liquid saturated vapor pressure at pump input is changed by heating. Periodical measurement of required parameters in process of liquid heating makes it possible to calculate sought for cavitation margin Δh. Method is implemented by test stand containing pump to be tested, output throttle, flow meter, heat exchanger, service tank, pipe fittings, all arranged in closed hydraulic circuit, and reservoir with free surface of working liquid in combination with capsule made of heat conducting material connected to circuit at pump input. Space of capsule is divided into two parts, one of which is partly filled with working liquid and sealed, and other communicates with circuit.

EFFECT: improved accuracy of measurements and simplified determination of pump cavitation characteristics.

3 cl, 1 dwg