流体动力学
一、流速

1. 流速

流体质点在单位时间内流过的位移，称为流速v

                     v=△s/△t

式中  v----流体的流速， m/s;

△s---流体质点的位移， m;

△t----流体质点位移 △s所经过的时间，s。

2.平均流速

在某一断面上，流速的平均值称平均流速vcp，工程计算上常用的是平均流速。对于流体的流速、流量和过流断面面积的关系，用以下公式表示。
对于质量流量q，可用下式表示:
                           q=ρFvcp

Vcp=q/pf

式中  q----质量流量，kg/s;

p----流体的密度，kg/m3 ;

F----过流断面面积，m2 ;

Vcp-平均流速，m/s。
对于重量流量G,可用下式表示:
                         vcp=G/yF
式中G---重量流量， N/s或kgf/s;
y---流体的重度，N/m2 或kgf/m3。

当液体流动时，温度和压力不变的情况下，其密度p和重度y是不变的，所以可以用体积流量来表示:

    Vcp=Q/F

式中Q----体积流量，m3/s
二、流体连续性方程
    由图1-3所示，在管道中，流体由1-1断面流入，2-2断面流出。 根据质 量守恒定
理，同一时间内流入的质量应该等于流出的质量。

式(1-12) 就是可压缩流体的连续性方程。

如果流体的密度ρ为常数时，即不可压缩流体，ρ1=P2
式(1-13)为不可压缩流体的连续性方程。
三、流体能量守恒定理-柏努利方程
    如图1-4所示，假设一股液流，从管道的1-1断面流入，经过2-2断面流出。若以0-0为基准线，则在1-1断面处:位置高度为Z1，平均流速为v1，压强为P1; 2-2断面处:位置高度为Z2，平均流速为2，压强为P2， 并且假设为理想流体，流体流动过程中没有摩擦力的作用，并为恒定流动，根据能量守恒的原理，就有下式
    这就是理想流体的柏努利方程，其几何意义是单位重量的液体在流动中，其位置水头Z,压强水头。及速度水头”。三者之和为-常数。 并且三者在流动过程中是可以互相转换的。
    但实际流体是有黏性的，液体在流动过程中流体之间有内摩擦阻力，流体与固体壁面之间也有摩擦力，这种摩擦力将会引起水头阻力损失，设为h_。则式(1-14)可写成:

这就是实际流体的柏努利方程。渣浆泵

fluid dynamics

I. velocity

1. velocity

The displacement of fluid particles in unit time is called velocity v

V= Delta s/ delta T

Where V is the velocity of fluid, M / S;

△ s --- displacement of fluid particle, m;

△ T ---- the time for the displacement of fluid particle △ s, S.

2. Average velocity

In a certain section, the average velocity is called the average velocity VCP, which is commonly used in engineering calculation. For the relationship between flow velocity, flow rate and cross-section area of flow, the following formula is used.

For mass flow Q, it can be expressed as follows:

Q= P Fvcp

Vcp=q/pf

Where Q - mass flow, kg / S;

P - density of fluid, kg / m3;

F - cross section area of overcurrent, m2;

VCP mean velocity, M / s.

For weight flow g, it can be expressed as follows:

Vcp=G/yF

Where g --- weight flow, N / s or kgf / S;

Y is the gravity of the fluid, N / m2 or kgf / m3.

When the liquid flows, and the temperature and pressure are constant, its density p and density y are constant, so it can be expressed by volume flow:

Vcp=Q/F

Where Q ---- volume flow, m3 / S

Fluid continuity equation

As shown in Figure 1-3, in the pipeline, the fluid flows in from section 1-1 and out from section 2-2 Keep constant according to quality

In the same time, the quality of inflow should be equal to that of outflow.

Equation (1-12) is the continuity equation of compressible fluid.

If the density ρ of the fluid is constant, i.e. incompressible fluid, ρ 1 = P2

Equation (1-13) is the continuity equation of incompressible fluid.

3. Conservation of fluid energy Bernoulli equation

As shown in Figure 1-4, suppose a stream of liquid flows in from section 1-1 of the pipeline and flows out through section 2-2. If 0-0 is taken as the reference line, at section 1-1: the position height is Z1, the average flow rate is V1, and the pressure is P1; at section 2-2: the position height is Z2, the average flow rate is 2, and the pressure is P2, and it is assumed that it is an ideal fluid, there is no friction in the process of fluid flow, and it is a constant flow. According to the principle of energy conservation, it has the following formula

This is Bernoulli's equation of ideal fluid. Its geometric meaning is the position head Z and pressure head of unit weight liquid in flow. And velocity head ". The sum of the three is - constant And the three can transform each other in the flow process.

But the actual fluid is viscous. In the process of fluid flow, there is internal friction between the fluid and the solid wall. This friction will cause the loss of head resistance, which is set as H UU. Formula (1-14) can be written as follows:

This is Bernoulli's equation for real fluids. Slurry pump