CN101799391A - Method for generalizing roughness of non-watertight matter in numerical simulation - Google Patents

Abstract

The invention relates to a method for generalizing the roughness of a non-watertight matter in a fluid numerical simulation, which comprises the following steps of: 1) performing a flume experiment to measure a water head difference, namely measuring the water head difference of the upper side and the lower side for a plurality of times, wherein the non-watertight matter in the original shape is used for performing experiments in a flume, and the water head difference is generated under a condition that the non-watertight matter is at different underwater penetrations and the water flow velocities are different; 2) establishing the relationship between the blocking proportion and the equivalent roughness of a micro-thick non-watertight matter in water, supposing that the length of an open channel is 11, converting the local water head loss caused by the micro-thick non-watertight matter into the on-way water head loss on an equal-length open channel, and calculating the equivalent roughness of on the section of the open channel; and 3) generalizing the non-watertight matter in a numerical model, and converting the equivalent roughness into the roughness of grids. The method adopts an original-shape non-watertight matter to perform the flume experiment so as to reduce errors in the process of zooming a physical model of the non-watertight matter, and provide a new train of thought for rating the roughness of a non-watertight matter with irregular eyelets and a non-watertight matter of which the properties are changed greatly in the using process.

Description

The method of the permeable thing roughness of generalization in the numerical simulation

Technical field

The present invention relates to a kind of in the fluid numerical simulation method of the permeable thing roughness of generalization.

Background technology

At present, determine to wait the method for the normal employing in field to have two kinds at permeable thing roughness: experimental formula method and in proportion or control with changed scale convergent-divergent physical experiments determination method; And the normal method that adopts of permeable generalization of thing roughness is generally the roughness methodology in the fluid numerical simulation.Above-mentioned three kinds of methods have characteristics and defective separately.

Experimental formula method: the material and the perforation size that need known permeable thing.But in practice, the shape of permeable thing may be irregular, permeable thing eyelet size, perforation density may be different, the newness degree of permeable thing may be different, the water permeability of permeable thing may be influenced by external factor change has taken place, perhaps eyelet is fine and closely woven, and permeable thing blocking proportion in water does not make on an equal basis and adopts the experimental formula method to exist than mistake; In addition, the development of various new materials also makes the use of experimental formula method have increasing difficulty.

In proportion or control with changed scale physical experiments determination method: the method maturation, but need usually permeable thing have clearer and more definite size and the shape of rule could require to carry out physical experiments behind the convergent-divergent according to the physical model guide.Permeable thing irregular or that the aperture is very little can't require to carry out convergent-divergent according to the physical model guide, is difficult to determine roughness by physical experiments.

Permeable thing roughness is generally changed method in the fluid numerical simulation: to having the permeable thing of certain volume, in the fluid numerical simulation, generally can adopt the roughness methodology generally to change, promptly the roughness by test or the permeable object that calculates of experimental formula be shared according to its volume ratio of actual shared volume (three-dimensional model) or area (two dimensional model) in fluid numerical value analogue computer.But,, can't directly adopt methodology because of being difficult to quantize the ratio of its actual shared volume or area in fluid numerical value analogue computer for the permeable thing of little thick any eyelet-like.

Summary of the invention

The technical problem to be solved in the present invention is to provide the method for the permeable thing roughness of generalization in a kind of numerical simulation, can realize the simulation that little thick permeable thing blocks water in the fluid numerical simulation easily.

The present invention is by the following technical solutions:

The method of the permeable thing roughness of generalization in a kind of numerical simulation may further comprise the steps:

1) flume test is provided with high and low water level advection district in tank, the filter screen district is located between the two advection districts,

A. permeable thing is fixed on that the degree of depth is d in the filter screen district ₁The place;

B. regulate the tank flow, measurement flow rate is at v ₁, v ₂... v _mDown, current are by the head difference p of permeable deposits yields ₁₁, p ₁₂... p _1m

C. the permeable thing of original state being fixed on the tank degree of depth is d ₂, d ₃... d _nThe place repeats above-mentioned steps 2), when writing down each degree of depth, different in flow rate is by the head difference p of permeable deposits yields ₂₁, p ₂₂... p _2m, p ₃₁, p ₃₂... p _3m... p _N1, p _N2... p _Nm

2) build the ratio that the blocks water-equivalent roughness curve of permeable thing,

A. suppose that open channel length is l ₁, the local head loss that filter screen causes is Δ H, the local head loss that permeable thing is caused is scaled the frictional head loss on the equal length open channel;

B. calculate the equivalent roughness n on this section open channel;

$n=\frac{{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000084886100012.png"\; state="\{\{state\}\}">R</figure-callout>}}^{2/3}{\mathrm{<figure-callout\; id="1"\; label="J"\; filenames="HSA00000084886100012.png"\; state="\{\{state\}\}">J</figure-callout>}}^{1/2}}{v}=\frac{{\left(\frac{w}{\mathrm{\&chi;}}\right)}^{2/3}{\left(\frac{\mathrm{\&Delta;H}}{l_1}\right)}^{1/2}}{Q}H$

In the formula, Q is a discharge per unit width, and H is the downstream section depth of water, and w is a discharge section area, and χ is a wetted perimeter;

C. by equivalent roughness and the ratio of blocking water are carried out numerical fitting, set up the ratio that the blocks water-equivalent roughness curve of permeable thing;

3) the permeable thing of generalization in the numerical model,

A. set up mathematical model, divide grid;

B. according to the ratio of grid length, will calculate gained equivalence roughness and be converted into the grid roughness with supposition open channel length;

C. carry out numerical simulation calculation.

Preferably, in the described step 1), adopt the permeable thing of original state to carry out flume test, described permeable thing eyelet is irregular.

Preferably, described numerical fitting is a fitting of a polynomial.

The present invention has following technique effect:

(1) adopt the permeable thing of original state to carry out flume test, need not to measure permeable thing aperture, reduced the error in the permeable thing physical model convergent-divergent process, for the permeable thing of irregular eyelet and in use character permeable thing roughness calibration that bigger change taken place new thinking is provided.

(2), permeable thing block water ratio and equivalent roughness relational expression have been set up by test of many group models and numerical value processing means.By the block water test of ratio of permeable thing difference, according to test findings, set up the relational expression of permeable thing equivalence roughness and the ratio that blocks water, make the result of test be applicable to the permeable thing of the ratio that blocks water arbitrarily; Under the identical situation of the ratio of blocking water, by the derivation of equation, set up the relational expression of the equivalent roughness and the depth of water, make the flume test result be applicable to any depth of water in the actual use.The permeable thing of little thickness exists in actual use than big-difference.This has proposed to adopt test and numerical value to fit the block water quantitative relationship of ratio and roughness of the method research that combines, and by methods such as numerical fittings, has set up block water relation formula with roughness of filter screen non-full section.

(3) method of roughness parameter generalization in the planar mathematical model of the permeable netted water-blocking material of little thickness has been proposed.Because the permeable thing thickness of little thickness is less, in the actual generalization process of digital-to-analogue, it can't be generalized as zone with certain roughness, this is by setting an open channel length, local head loss is converted into frictional head loss, makes the flume test achievement can be directly applied for grid big or small arbitrarily in the two-dimentional pattern of water flow.

Description of drawings

Fig. 1 is the general flow chart of the method for the permeable thing of generalization in the numerical simulation involved in the present invention.

Fig. 2 is the structural representation of tank in the method for the permeable thing of generalization in the numerical simulation involved in the present invention.

Embodiment

In conjunction with Fig. 1, the present invention includes following steps:

One, flume test is measured head difference

1) the permeable thing of original state being fixed on the tank degree of depth is d ₁The place;

2) regulate the tank flow, control is by the flow velocity of permeable thing, and measurement flow rate is at v ₁, v ₂... v _mDown, current are by the head difference p of permeable deposits yields ₁₁, p ₁₂... p _1m

3) the permeable thing of original state being fixed on the tank degree of depth is d ₂, d ₃... d _nThe place repeats above-mentioned steps 2), when writing down each degree of depth, different in flow rate is by the head difference p of permeable deposits yields ₂₁, p ₂₂... p _2m, p ₃₁, p ₃₂... p _3m... p _N1, p _N2... p _Nm

Permeable thing is tested the upper and lower sides head difference that the permeable thing difference of many groups time mensuration underwater penetrations produce with original state under different flow rate of water flow conditions in tank.

Two, set up little thick permeable thing blocking proportion and equivalent roughness relation in water

1) supposition open channel length is l ₁, the local head loss that filter screen causes is Δ H, the local head loss that permeable thing is caused is scaled the frictional head loss on the equal length open channel, can inquire into the graceful peaceful roughness of corresponding equivalence based on Chezy formula (formula 1) and Manning formula (formula 2);

$v=C\sqrt{\mathrm{RJ}}---\left(1\right)$

In the formula,

V is a mean velocity in section;

C thanks to the ability coefficient and inquires into based on Manning formula (formula 2) for thanking to just coefficient;

R is a hydraulic radius, is the ratio of discharge section area w and wetted perimeter χ;

J is a hydraulic slope, is open channel water surface unit distance drop, equals to take place the upstream and downstream side water-head of frictional head loss and the ratios delta H/l of its length L ₁

$C=\frac{1}{n}{R}^{1/6}---\left(2\right)$

N is a Manning roughness coefficient in the formula;

2) calculate equivalent roughness on this section open channel by hydraulic formula, formula (2) substitution formula (1) can be got the graceful peaceful roughness computing formula of filter screen equivalence:

$n=\frac{R^{2/3}{\mathrm{<figure-callout\; id="1"\; label="J"\; filenames="HSA00000084886100012.png"\; state="\{\{state\}\}">J</figure-callout>}}^{1/2}}{v}=\frac{{\left(\frac{w}{\mathrm{\&chi;}}\right)}^{2/3}{\left(\frac{\mathrm{\&Delta;H}}{l_1}\right)}^{1/2}}{Q}H---\left(3\right)$

In the formula,

Q is a discharge per unit width;

H is the downstream section depth of water;

W is a discharge section area;

χ is a wetted perimeter;

3),, draw the block water relation of ratio and equivalent roughness of the permeable thing of little thickness by means such as numerical fittings by the relation of respectively block water ratio and equivalent roughness.

Three, the little thick permeable thing of generalization in the numerical model

1) set up mathematical model, on a certain size grid, grid length is l with permeable generalization of thing ₂

2) according to the length l of grid ₂With supposition open channel length l ₁Ratio, will calculate the roughness that gained equivalence canal roughness is converted into grid;

${\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="HSA00000084886100012.png"\; state="\{\{state\}\}">n</figure-callout>}}_2={\left(\frac{l_1}{l_2}\right)}^{1/2}*n_1---\left(4\right)$

In the formula,

n ₁Be supposition open channel length l ₁Equivalent roughness;

n ₂Be the grid length l ₂Equivalent roughness;

3) carry out numerical simulation calculation.

Fine and close filter screen as an interception blue-green algae is used is placed on certain depth under water, and for non-full section blocks water, in the filter screen long period of soaking water, the part mesh is stifled by silt.

Please refer to shown in Figure 2ly, tank comprises three zones, is followed successively by the first advection district 1 from left to right, and the surface level in 2, the first advection districts 1,3, the second advection districts, filter screen district is than the second advection district, 2 height, and filter screen 4 is located in the filter screen district 3.At first, make difference block water ratio filter screen and framework, periphery is spread silica gel seal antiseepage and handle, with the steel folder filter screen is fixed on the tank then, make it to be kept upright, regulate the tank flow, control is by the flow velocity of filter screen;

Then, carry out many group tests, measure the different in flow rate current by the difference head difference that the ratio filter screen produces that blocks water;

Then, suppose the open channel length l ₁(as l ₁Be 100m), the local head loss that current are produced by filter screen is converted into the frictional head loss on the open channel length;

Then, calculate equivalent roughness on this section open channel by hydraulic formula;

In generalization of mathematical model, with generalization of filter screen on the grid of certain-length, according to the length l of grid ₂With supposition open channel length l ₁Ratio, carry out Model Calculation with calculating the roughness that gained equivalence canal roughness is converted into grid.

The present invention is owing to adopt the original state filter screen to carry out physical test, successfully solved block water definite method of roughness of filter screen.When carrying out physical test, be difficult to accurately measure the filter screen aperture and find the filter screen equivalent material that can be used for testing, this adopts the original state net to carry out flume test, error and at utmost realistic operating mode in the filter screen thing mould convergent-divergent process have been reduced, for solving the problem that directly to inquire into roughness by formula, derive by block water Mechanism Study and hydraulic formula of filter screen, make the result of flume test directly to apply in the two-dimentional pattern of water flow, and can reflect the present situation operating mode preferably.

In addition, by system model test and the match of polynomial expression numerical value, set up the non-full section of filter screen and blocked water and the roughness relational expression.Filter screen is placed under water the degree of depth according to actual conditions difference to some extent, and the degree that blocks water also there are differences according to the difference of water level and underwater topography everywhere.This has proposed to adopt test and numerical value to fit the block water quantitative relationship of ratio and roughness of the method research that combines, by the inferior flume test of matrix form combination group, in conjunction with polynomial expression numerical value approximating method, set up block water relation formula with roughness of filter screen non-full section.

Also have, the present invention proposes the method for roughness parameter generalization in the planar mathematical model of the permeable netted water-blocking material of little thickness.Because filter screen thickness is less, in two-dimentional generalization of digital-to-analogue, it can't be generalized as the zone with certain roughness.The present invention is by the hydraulics theoretical derivation, the local head loss that the part section is blocked water generally changed into the net loss of flood peak and streamed the loss of flood peak, and by setting an open channel length, local head loss is converted into frictional head loss, makes the flume test achievement can be directly applied for grid big or small arbitrarily in the two-dimentional pattern of water flow.

The foregoing description is the unrestricted method scheme of the present invention in order to explanation only.Any method scheme that does not break away from spirit and scope of the invention all should be encompassed in the middle of the patent claim of the present invention.

Claims (3)

1. the method for the permeable thing roughness of generalization in the numerical simulation is characterized in that may further comprise the steps:

1) flume test is provided with high and low water level advection district in tank, the filter screen district is located between the two advection districts,

A. permeable thing is fixed on that the degree of depth is d in the filter screen district ₁The place;

B. regulate the tank flow, measurement flow rate is at v ₁, v ₂... v _mDown, current are by the head difference p of permeable deposits yields ₁₁, p ₁₂... p _1m

C. the permeable thing of original state being fixed on the tank degree of depth is d ₂, d ₃... d _nThe place repeats above-mentioned steps 2), when writing down each degree of depth, different in flow rate is by the head difference p of permeable deposits yields ₂₁, p ₂₂... p _2m, p ₃₁, p ₃₂... p _3m... p _N1, p _N2... p _Nm

2) build the ratio that the blocks water-equivalent roughness curve of permeable thing,

A. suppose that open channel length is l ₁, the local head loss that filter screen causes is Δ H, the local head loss that permeable thing is caused is scaled the frictional head loss on the equal length open channel;

B. calculate the equivalent roughness n on this section open channel;

$n=\frac{R^{2/3}{J}^{1/2}}{v}=\frac{{\left(\frac{w}{\mathrm{\&chi;}}\right)}^{2/3}{\left(\frac{\mathrm{\&Delta;H}}{l_1}\right)}^{1/2}}{Q}H$

In the formula, Q is a discharge per unit width, and H is the downstream section depth of water, and w is a discharge section area, and χ is a wetted perimeter;

C. by equivalent roughness and the ratio of blocking water are carried out numerical fitting, set up the ratio that the blocks water-equivalent roughness curve of permeable thing;

3) the permeable thing of generalization in the numerical model,

A. set up mathematical model, divide grid;

B. according to the ratio of grid length, will calculate gained equivalence roughness and be converted into the grid roughness with supposition open channel length;

C. carry out numerical simulation calculation.

2. the method for the permeable thing roughness of generalization in the numerical simulation according to claim 1 is characterized in that: in the described step 1), adopt the permeable thing of original state to carry out flume test, described permeable thing eyelet is irregular.

3. the method for the permeable thing roughness of generalization in the numerical simulation according to claim 1 is characterized in that: described numerical fitting is a fitting of a polynomial.

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