Questions tagged [fluid-mechanics]

Questions relating to fluids at rest (fluid statics) or the forces and effects of fluids in motion (fluid dynamics).

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5 votes
3 answers
675 views

Buoyancy force problem

I'm trying to design a kind of water valve with inexpensive materials as a first prototype. The water flow from the PVC pipe (1) reach the body of the valve and pass through an aluminum grid (3) to ...
0 votes
2 answers
140 views

Static Head Assumptions

I have questions about a well pump application I am working on. It consists of a well that with a submersible pump that fills a reservoir tank. As far as I know, the tank is not pressurized. Here are ...
0 votes
0 answers
22 views

How (mathematically) does pressure in the intake manifold vary based on size of throttle opening?

I have the intuitive picture somewhat down: the intake manifold is partially opened; during the intake stroke of a four-stroke process, the piston moves rapidly moves downwards creating a short-term ...
0 votes
1 answer
41 views

Pressure variation through reduction (Bernoulli) and pipe wall design

Let's say I have a pipe followed by a reduction and then another smaller diameter pipe continues. Using conservation of mass, the flow through the smaller diameter pipe will have higher velocity. If I ...
0 votes
0 answers
24 views

Employing a deforming mesh, inlet, and no shear wall in ANSYS

I am interested in running a simulation in ANSYS Fluent (or CFX, whichever is more useful) that combines the following. Update: A rotating wing in the air, similar to a turbine blade. After ...
0 votes
2 answers
59 views

Interpretation of dx/dt and u in CFD

I am currently studying CFD and I have a question about how I should interpret the term u and dx/dt. I would like to find that out in the textbook, but I could not. When I solve 1D Euler Equation with ...
0 votes
1 answer
59 views

Increasing airflow of fan

I learned at at young age from a physics kit that one can blow up a large bag with your mouth by blowing into it from a distance and letting the air pick more air with it. Later in life when Dyson ...
1 vote
2 answers
53 views

Airflow visible over the airplane wing

What's that visible airflow over the airplane wing and what causes it?
0 votes
2 answers
630 views

How to calculate the viscous damping coefficient given drag force

Force due to drag at low velocities, is equal to some constant times negative velocity $$F_{d}=-c_{1}V$$ The viscous damping coefficient equals decay constant divided by 2 times mass $$\gamma = \...
2 votes
1 answer
56 views

Component selection type for fluid-mechanical system

I am creating an enclosure and need to get a water supply through a plastic wall inside to the core device. I imagine this water line will be a flexible tube and will screw on or snap to an adapter on ...
1 vote
2 answers
746 views

Find Torque and Force on Pipe with Bend

I did a Civil Engineering course some years ago and from my textbook I had a question on a pipe with a bend. Now I think I have the part of the question on force correct, but I am not sure how the ...
0 votes
1 answer
170 views

What is the force needed to exert on the piston for a certain extrusion rate of a syringe tube?

I am trying to design a syringe pump for microfluidic extrusion uses. I have a 5cc syringe tube that I will use as the cartridge. We would be using it to extrude a variety of materials so the ...
2 votes
0 answers
19 views

Consistent Fluid or powder flow through an orifice

This is a really odd and specific question, and I'm not sure this is even where to ask. A few weeks ago I thought about making a clock based on water flowing from an orifice. The obvious issue is that ...
1 vote
1 answer
155 views

Boundary Layer Thickness for Flat Plate

I did a Civil Engineering course some years ago and from my textbook I had a question on boundary layer thickness. So far I have been able to calculate the transition distance, but I am not sure how ...
1 vote
1 answer
221 views

Pipe network analysis: static pressure of a closed-loop pipe

I've learned fluid dynamics but does not have much knowledge about its real-world applications. My question is about the static pressure of a closed-loop pipe. [Fig. 1. Pipe network. Source: ...
1 vote
4 answers
88 views

Can I create a whirlpool/vortex around a horizontal axis in a flat bottle using motor?

I am using this flat bottle: I fixed a motor at the centre of one of the flat sides and attached an impeller. I thought this will create some kind of whirlpool effect but as you can guess, since the ...
0 votes
2 answers
225 views

Boundary layer thickness decreases as fluid velocity increases, so why is the boundary layer thicker in the turbulent region for higher velocities?

I am modelling transitional fluid flow over a flat plate, and investigating the effects of free stream velocity on boundary layer thickness. From what we have been told, increasing free stream ...
3 votes
3 answers
1k views

Free falling fluid pressure distribution

Consider a free falling tank of fluid. The goal is to find the pressure distribution. My intuition says that there should be no pressure distribution; the pressure should be uniform since the ...
0 votes
1 answer
53 views

Could a hybrid system of mechanical levers and hydrostatic/hydraulic cylinders be able to lift 200+ kg with the force of an arm?

I don't know much about levers and hydrostatic/hydraulics myself, so I hope I don't make too many misconceptions. The idea: Hypothetically, if you had a 40km+ long indestructible lever on a ...
1 vote
1 answer
90 views

Pressure drop in a CFD simulation of an air flow too small

I am simulating a turbulent air flow through a rectangular channel with the goal to match measured velocity profiles and the static pressure at certain points. My problem is that the pressure drop in ...
4 votes
4 answers
661 views

Direction of fluid flow

Consider water flowing in a pipe, and I don't know the direction of flow. How to determine the direction of flow? My approach- I can use a pitot tube but for that I have to drill a hole in the pipe ...
0 votes
1 answer
58 views

Low-Flow Nozzles for Corrosion Spray Testing

So, for a cyclic corrosion test system, I need a nozzle or arrangement of nozzles that provides a flow rate of 45ml-140ml of salt solution per hour to an area 60cm square. All commercial nozzles I've ...
2 votes
2 answers
64 views

Imposing/ensuring a constant mass flow rate in turbulent flow simulation

I'm trying to simulate using Finite Elements (non commercial software) the Tube Bundle benchmark problem: http://cfd.mace.manchester.ac.uk/ercoftac/doku.php?id=cases:case078&s[]=tube&s[]=...
0 votes
2 answers
47 views

Flow of fluid in branched pipes

Could any one please tell me if there is any flow possible into pipe 2. What I believe is that as pipe 1 and pipe 3 are of same diameter and applying Bernoulli's equation between points 1 and 3 gives ...
0 votes
1 answer
30 views

Ball immersed into a fluid

A plastic ball is pushed inside the tank and then released, can anyone plot velocity vs time and velocity vs height as long as ball is completely inside the water? For simplicity we can assume no ...
0 votes
1 answer
31 views

What is a good working fluid in the temperature range of 150 - 180 °F?

I am looking for a good working fluid whose boiling point is in the range of 150 - 180 °F for a waste heat recovery system. The fluid should be minimally flammable, preferably nontoxic, and low in ...
0 votes
0 answers
14 views

Meshing edges in Star CCM+ for CFD simulation

I am doing a CFD study on a bluff body to study the drag variation. During the meshing process in Starccm+ I came across a stage where the mesh does end smoothly at the edge (see figures). Which ...
0 votes
0 answers
19 views

Analytical / Experimental calculation of pressure loss for simple crossflow of air across a simple cylinder

I need a way to find pressure loss of air flowing across a single tube for both laminar and turbulent flows. I have referred to several sources (Y. Cengel Heat and Mass Transfer and Fluid Dynamics ...
0 votes
0 answers
8 views

At what location in a ducted centrifugal fan, the discharge of which is turned from radial to axial via the duct, is the force of thrust applied?

I am optimizing the structure of the duct for weight savings and need to know where the force of thrust (load) will be located. Assume the inlet is at the top, the fan axis of rotation is vertical. ...
1 vote
2 answers
211 views

Calculating Minimum Pipe Pressure Requirement for an Irrigation System

I am setting up an irrigation system for my ranch and I have a hard time calculating the minimum pipe pressure requirements to reduce cost. I need to know the maximum pressure the pipe has to cope ...
0 votes
2 answers
150 views

Assessing flow rate from open sea into a container

I'm currently assessing sub sea pumped hydro capabilities, and need to use the flow rate in order to calculate power output. I can calculate the energy storage capacity using E = mgh: $E=mgh = ...
0 votes
1 answer
290 views

How much water do steam turbines consume per kWh of electricity generated?

I know this depends on some factors, and I can only think of these: the inlet steam's temperature and pressure. If there are more factors then please do tell me. What is the maximum figure in liters ...
0 votes
0 answers
31 views

Is there a CFD program that can simulate the motion of a non rigid body through fluid?

Is there a CFD program that can simulate motion of a conveyor belt underwater? Aproximating it as a moving rigid plate is not gonna work.
1 vote
3 answers
325 views

How can I connect F=ma to Drag=1/2*Cd*(rho)*V^2*A?

I previously posted a different question that was very vague. I have kept working on the problem, and now I have a different question. Please let me know if I should have just added it to the old ...
1 vote
1 answer
46 views

What is the side way force on a flat membrane place perpendicular to the flow of current on one side, and stagnant water on the other

So basically imagine a plate being placed parallel to the direction of flow of water with water flowing with a certain velocity on one side of the plate and on the other side it is almost stagnant. ...
1 vote
2 answers
190 views

Deriving the ideal equation for sluice gate problems - incompressible inviscid fluid

I'm trying to figure this problem out, i know the correct answer, and i know the method, but for some reason i'm missing something and i'm just not getting there, any help would be greatly appreciated....
1 vote
2 answers
190 views

converting air flow rate between l/min to kg/s

I am calculating the air mass flow rate in kg/s for air in a numerical model, and i want to compare the results with an experimental investigation, the flowmeter unit is l/min. how can I convert l/min ...
2 votes
1 answer
101 views

Generating Linear Velocity Movement?

In preparation for a Fluid Mechanics experiment, I am looking for a simple commercial ready made apparatus to generate a linear velocity trend to prove a new theory: https://aip.scitation.org/doi/abs/...
0 votes
1 answer
80 views

Is the metacentric height independent of heel angle?

when the sides of a pontoon are verticle, BM(distance between center of buoyancy and metacenter) is given by I/V As well as for a small angle that expression is true. But when the heel angle ...
1 vote
1 answer
55 views

Normal Shockwaves occurrence at cone tip with Angle Theta

I have a question regarding shockwaves. So as far as my knowledge, a flow moving at Ma= 1 will create a normal shockwave ($arcsin(1/Ma)$) , and a flow moving faster will cause an oblique shockwave. So ...
0 votes
0 answers
33 views

Inaccurate flow rate measurements of an engine diesel fuel due to change of its viscosity

I am measuring the volumetric flow rate of a diesel fuel using "Turbines" flow meter, both in the supply and return fuel lines of an industrial diesel engine (Caterpillar 3512B – coupled ...
0 votes
2 answers
52 views

Discharge at an angle in a channel concept question

Now I agree that the velocity of the discharge and the area is not at right angles, but I don't understand how using $\cos \theta$ helps? Shouldn't I use the area perpendicular to the channel? Like so:...
1 vote
3 answers
90 views

Lift and drag force measurement in a flume

I'm trying a test a hydrofoil in a low Reynolds flume, but struggling to find a way to mount the hydrofoil in the flume and measure the lift and drag force. I have some idea of using a load cell but ...
0 votes
2 answers
54 views

Economical difference with high-pressure vessel design pressures for fixed volume

Suppose space is not an issue and I need a fixed volume of compressed air (for storage), say 1m³. Is it more economical to manufacture a thick-walled vessel but with a smaller volume or a thin-walled ...
0 votes
1 answer
96 views

What is the effect of different ways to adding liquid materials into a mixing tank?

I am working with body wash products and there is a problem happening with the mixing process. I use a 5000-liter tank to mix all the liquid materials including water, surfactant and preservatives. ...
0 votes
1 answer
107 views

Glide Ratio of an unpowered "sub"

Flying gliders can have glide ratios (ratio of horizontal distance vs vertical distance) around 50 or 60. How would that change when the fluid density changes, in particular under water. Could a ...
0 votes
1 answer
35 views

How to determine time taken for tyre to deflate using CFD analysis?

I am working on my final year project, and am at a point which requires us to deflate a tyre in 0.8 seconds. This needs to be simulated using CFD. We have drilled a hole into the rim and attached a ...
4 votes
3 answers
306 views

How to calculate the force that a liquid creates on the wall of an underground reservoir

I would like to calculate the force exerted on the wall of an underground reservoir. The volume of rocks surrounding the reservoir creates a force equal to the product of the density of the ...
0 votes
2 answers
920 views

Open pipe and relation between pressure and flow rate

If a pipe (of unknown/arbitrary length) with cross section area $A$ and with a continuous supply of a simple fluid with a known pressure $p$ at the opening to the atmosphere, which has a pressure of $...
1 vote
1 answer
27 views

Why is the exit loss $\frac{u^2}{2g}$ is small for laminar flow?

I have done some calculations: My lecturer just said that exit loss $\frac{u^2}{2g}$ is small for laminar flow so ignore it. But never explains why it is small?

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