Fluid Lab

What is 1 bar in meters head?

1 bar = 10.1997 meters head 1 meter head = 0.098 bar

What are the two types of losses in piping systems?

1. Losses due to friction in the pipes (viscous resistance extending throughout the total length of the circuit) 2. Losses causes by elbows also known as minor losses (localized effects such as valves, bend, and sudden changes in area)

What is a rotameter?

A rotameter consists of a tapered tube, typically made of glass with a 'float' (a shaped weight, made either of anodized aluminum or a ceramic), inside that is pushed up by the drag force of the flow and pulled down by gravity.

What is capillarity?

Capillarity may be defined as rise or fall of a liquid in a tube. The phenomenon of rising water in a tube of smaller diameter is called capillary rise. ht = 4*sigma/rho*g*d

For pumps in parallel, the flow rate is ___ and the pressure head is ___.

For pumps in parallel, the flow rate is 2Q and the pressure head is H.

For pumps in series, the flow rate is ___ and the pressure head is __.

For pumps in series, the flow rate is Q and the pressure head is 2H.

What is Reynolds' number?

It is a non-dimensional parameter that expresses the ratio of inertia to viscous forces and can be used to identify the conditions under which the flow changes from laminar to turbulent.

What is a gate valve?

It is a valve used for opening and closing a fluid passage and consists of a gate or disc which can be moved up and down across the line of flow by, a handwheel. It is the most common, cheapest but also the least accurate valve.

In losses in piping systems, where is K not a constant?

K is not constant for valves since the geometry of these components changes when opening and closing them. For all other components, K is a constant because their geometry doesn't change.

What is the formula for the hydraulic jump?

Lj = 5(y2-y1)

In a real life situation, what do you think might be some of the advantages of using two pumps together instead of using one larger pump?

One major benefit of parallel pumping is the high degree of standby capacity provided by single pump operation. When one pump is out of operation, the other pump continues to pump water through the system. But the flow rate isn't cut in half just because only one pump is operating.

Hydraulic power P0

P0 = mdot*g*H = rho*g*Q*H omega = 2*pi*N/60 Q = volumetric flow rate (m3 /s) P = power (W) N = speed (revs/min) H = head (m) rho = density (kg/m3 ) g = acceleration due to gravity (9.81 m/s2 )

How can we find the efficiency of the pump?

P0/Pi

Mechanical power input for a centrifugal pump

Pi = omega*T T = torque omega = angular speed (rad/sec)

In losses in piping systems, can we compare h1 and h4?

Piezometric heads that aren't connected to the same air pressure cannot be compared.

Total pressure = ?

Pressure = Delivery pressure - Suction pressure

What is the continuity equation?

Q = V1*A1 = V2*A2

What is the formula for Reynolds' Number?

Re = rho*V*D/mu = V*D/nu rho = density V = velocity D = pipe diameter mu = absolute viscosity of water nu = coefficcient of kinematic viscosity

How can we determine the end of a hydraulic jump?

Right at the end of the jump, the red dye droplet will sink to the bottom and move forward.

Which component results in a pressure gain instead of a pressure loss?

The Expansion is the component which results in a pressure gain. Q = VA, and we are increasing the area of the flow (small diameter pipe -> bigger diameter pipe)

What is a venturi meter?

The Venturi meter is a device used for measuring the discharge along a pipe. The fluid flowing in the pipe is led through a contraction section to a throat, which has a smaller cross-sectional area than the pipe, so that the velocity of the fluid through the throat is higher than that in the pipe. This increase in velocity is accompanied by a fall in pressure, the magnitude of which depends on the rate of flow, so that by measuring the pressure drop, the discharge may be calculated. Beyond the throat, the fluid is decelerated in a pipe of slowly diverging section.

What type of material are the pipes in the lab made out of?

The dark and light blue circuits are made out of copper.

What is density?

The density or mass density of a fluid may be defined as the mass per unit volume at a standard temperature and pressure. mass/volume (kg/m^3)

What does f depend on?

The frictional factor f depends on the type of material of the pipe and its roughness. These values can be found in tables and are constants. f = 2*hL*d*g / L*V^2

What is a hydraulic jump?

The hydraulic jump is a rapid and highly turbulent transition from flow at a low stage - below critical depth, to flow at a high stage - above critical depth. During this transition, the velocity changes from the supercritical to the subcritical state. The turbulence generated in the hydraulic jump results in a significant energy loss.

What is vena contracta?

The narrowest portion of the jet, it is located to the right of the small opening.

What is the difference between a standard 90° elbow and a miter 90° elbow?

The standard 90° elbow has a certain radius of curvature whereas the miter 90° elbow is very sharp and is rarely used. Both of them are separate components that are attached to the pipe usually by welding them, as opposed to bends where the pipe itself is bent.

How do we read the pressure head on valves?

The valves are connected to a pressure gage because the pressure is too high to be read in piezometric tubes since we would need the tubes to be a lot longer.

What is a globe valve?

This valve consists of a threaded spindle connected with a disc which seats on an opening provided in the middle of the valve. This opening is such that it causes a change in the direction of flow. It is more accurate than the gate valve.

Total Head =?

Total Head = Delivery Head - Suction Head

How can we find the density of an irregularly shaped solid?

Using a Eureka can

How can we find the flow rate if we get readings in mm from a rotameter?

Using the rotameter curve

What is Bernoulli's equation for an orifice plate?

Vf^2/2g - Ve^2/2g = K^2(he-hf) K = 0.601 coefficient of discharge

How can we go from laminar flow to turbulent flow?

We can either increase the velocity, or decrease the viscosity of the fluid by increasing the temperature.

What is the Venturi effect?

When there is a constriction in a tube, the velocity of the fluid will increase at that point while the pressure will be lower.

Minor losses are a measurement of head loss in the system due to? a) Friction loss in pipe fittings b) Low flows c) Measurement inaccuracies d) Friction losses in the pipeline

a) Friction loss in pipe fittings

What is the piezometric head equal to?

h = z + p/gamma z = elevation head p/gamma = pressure head

Bernoulli's Equation

h1 + V1^2/2g = h2 + V2^2/2g + hL hL: head losses

Minor losses equation

hL = K (V^2/2*g) K: dimensionless coefficient of pipe fittings V= Velocity of flow

Frictional Losses Equation (Darcy-Weisbach)

hL = f (LV^2)/2dg f: frictional factor L: length of the pipe V: velocity of the fluid d: diameter of the pipe g: gravitational acceleration

How can we calculate the head losses for a straight pipe connected to an elbow?

hL = f l V^2 / 2dg + K V^2 / 2g head of frictional losses in the straight pipe + head of frictional losses caused by the elbow

What is viscosity?

the resistance of a liquid to flow

In a hydraulic jump experiment, what are y1, y2 and Lj?

y1: supercritical depth y2: subcritical depth Lj: length of the jump

What is the formula for the subcritical depth?

y2 = (y1/2)*(sqrt( 1 + (8q^2)/g*y1^3)-1) q = discharge (cm^3/s) / width (30 cm)