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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Confusion between Steady flow and Space-Time invariant density field

Let's take the example of a steady flow with velocity field as $u=βr(\tilde{r})$. Now, we can find a density field $ρ(r,t)$ that satisfies the mass conservation equation of $∂ρ/∂t+∇(ρu)=0$. First, ...
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Pre requisites for a course in Heat Transfer from Fluid Mechanics , for a Mechanical Engineering Bachelors Degree [closed]

Can anyone please tell me the topics I need to study from Fluid Mechanics, specially fluid dynamics to understand Heat Transfer in a better way?
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Efflux velocity for system with air and liquid

I want to calculate the efflux velocity for this open vessel with area $A_1$ with a small outlet with area $A_2$ as a function of time. The atmospheric pressure is $p_0$. The vessel has height $h = h_{...
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Valve solution for mixing external air into a closed loop climate controlled air circulation system

I'm looking for an electronically controlled air valve solution which would provide a way to mix external air into a closed loop air circulation system used for climate control in an enclosure. The ...
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Using venturi effect for equilibrating pressure drop

Let me first say I am a novice in fluid dynamics, I am not sure about terminology but I will try to explain myself as clearly as possible. I need some help for understanding the following case: in a ...
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How to simulate gas-liquid mixing in a bioreactor in ANSYS Fluent?

I thank you for taking a look. I'm a beginner with so much love to simulate fluids as fluid visualizations fascinate me. My learning has been only through youtube, forums. So, please excuse my naivety ...
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3answers
52 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 ...
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68 views

Why is the theoretical formulation not explaining why the graph of the square of the velocity and angular displacement is nonlinear (experimentally)?

So I did a wind tunnel experiment where I put a rope restrained (1 degree of freedom, so it can wave in the direction of the wind) at one end so that it displaces according to the variation in wind ...
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55 views

Frictionless flow in pipes

I am trying to understand the flow of an ideal, frictionless incompressible fluid through a pipe for these two cases. Note: Please consider Flow velocity in the tank is zero, and the fluid is ...
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74 views

How do you imagine momentum?

If you want to explain it to a layman (who belongs to the science stream ofc!!) how do you explain it? Also, what is momentum transfer when it comes to fluid mechanics?
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How does shear/viscous stress change in liquids as applied shear force is changed?

As per Newton's law of viscosity, the dynamic viscosity of a Newtonian fluid is constant (doesn't change with applied shear stress).Consider the Couette flow used to explain viscosity . Whenever we ...
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Watering utility that does not spill

I saw a video showing a water bowl for a cat that used an upside down PET bottle to provide "fresh" water when cats consume some of the water in the bowl. I wanted to design something ...
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43 views

How to select a fan blade for my application (strong, focused breeze)

My question is how fan blade design relates to the focus of the air leaving the fan. I am looking to generate the most focused breeze I can with a fan blade, excluding additional ducting etc, the fan ...
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What is the velocity of a fluid particle at the center of a infinitely long counter-rotating vortex pair?

Let's take circulation strength of each vortex τ and distance between them is r. I feel the answer should be 2τ/πr but my friend is arguing its τ/2πr. So my thought process goes like, if you have a ...
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Water fountain laminar flow options using a 3d printer - can the default be significantly improved on?

I don't know if this is the right place to ask, but it is the best I can find! Laminar flow from a garden hose: All of the YouTube DIYs show a PVC pipe with the same sequence: Some sort of evener-...
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1answer
51 views

How to calculate head loss in vertical pipe?

I have used the Hazen-Williams equation to calculate head loss for falling water in a vertical pipe I am using in a hydroelectricity project of mine. Hazen-Williams equation: These are the properties ...
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87 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: ...
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30 views

Is this value of critical Reynolds number also valid for ducts?

In internal flow, when a fluid flows inside a circular pipe, the most practical value of critical Reynolds number is taken as 2300. I was wondering if this number is also the same for non circular ...
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Fluid Dynamics - Auto filling a reservoir to a constant water-level

I have created a reservoir that is intended to automatically self-fill at exactly 1/4" depth. The idea is that the reservoir is hooked up to the airtight jug and dispenses the liquid until the ...
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Why is a throttling valve isenthalpic whilst a nozzle is not?

From my understanding, Nozzle's and throttling valve are devices which both trade pressure for velocity, so they increase velocity at the expense of having to decrease the pressure. If we examine ...
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81 views

Is Bernoulli’s equation applicable for systems with pumps?

Please have patience with me as I have not looked at this sort of theory in many years (I am also very new to StackExchange). A question asks the following: A sloping swimming pool two-thirds full of ...
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1answer
64 views

How to mix pure CO2 with air so that a bioreactor can be fed with air at 0.1% to 10% CO2?

The situation is we have to prepare a gas mix of air and CO2 which has to be given as input from 0.1% to 10% CO2 of air mix to the aqueous medium in a bioreactor? I'm trying to build a simple and ...
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4answers
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Balancing suction air flow at different areas on pipe

I have a T-shaped pipe that is connected to a vacuum pump. Along one side, there are 4 areas of 9 holes where air will get sucked in from the surroundings. It's used to pick up some small objects. The ...
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68 views

How can I make a vacuum pump to move rocks from one place to another?

I am trying to build a vacuum pump by myself and move rocks from one place to another. After some online search, I came across this video on Youtube. I am trying to build something like this. Can ...
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1answer
72 views

Is a no-moving-parts air pressure transformer possible?

Is it possible to construct a solid state fluid system (tubing, channels, chambers, nozzles, etc.) that can convert the energy from a low-pressure high-flow-rate air current into a high-pressure low-...
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Book recommendation for hydrodynamics of bubbles, drops, and particles

I am wondering if someone could please recommend to me some references on the topic of hydrodynamics of bubbles, drops, and particles, preferably in the context of complex and bio fluids. I am ...
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Is NPSHr dependant on temperature?

I know that net positive suction head available depends on temperature since viscosity, density and vapour pressure depends on temperature but how about NPSHr? We know that the vapour pressure depends ...
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2answers
41 views

Can I dismiss wind loads for this solar panel configuration?

I asked this question before in the Physics Stack Exchange, but it was closed because it was considered being about engineering. That is why I am asking it here. I am planning to install some solar ...
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1answer
41 views

Need help on conservation of momentum (liquid jet) Problem!

I had a quick question regarding this homework problem, I can't seem to understand why they chose to use the conservation of momentum in vertical direction and not the horizontal direction as you ...
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1answer
40 views

Analytical solution for the 1D convection-diffusion equation

The Ogata and Banks analytical solution of the convection-diffusion equation for a continuous source of infinite duration and a 1D domain: where C [mol/L] is the ...
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Non-Dimensionalizing Navier-Stokes equation to derive the Thin-Film Equation

I want to start with the general Navier-Stokes equation in 3-D: $$ \frac{\partial \vec{u}}{\partial t} + (\vec{u}\cdot\nabla)\vec{u}=-\frac{1}{\rho}\nabla p+\frac{\mu}{\rho}\nabla^2\vec{u}+g\sin{\...
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What is a safe and efficient temperature range for absorption chiller generators?

I've read that the role generators play in the absorption chiller cycle is to concentrate the salt solution so that the evaporator/absorber can maintain a vacuum by constant absorption of vapour ...
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How Do I Calculate the Velocity of the Flow That Is Sucked Into Two Parallel Walls by a Fast Moving Flow?

I'm trying to solve a problem where I calculate the velocity of the setup bellow. Basically I have two very long(basically infinite for calculation purposes) plates, and I have one central jet of gas ...
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87 views

In which bucket , should the water fill it up first?

Here , we have two water filters and buckets . Now , we know that as the water falls down , it’s speed increases because of acceleration due to gravity. Let us say I started both the filters and once ...
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44 views

Angular Velocity And Flow Rate Relationship Of Turbine

I was designing a turbine to be utilized in order to measure the flow rate of a river system. I can measure the angular velocity of the shaft by utilizing a magnet and hall sensor, however, in order ...
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194 views

Given flow rate of an orifice at one pressure, how do I calculate flow rate for a different pressure?

Given an orifice rated 1.8 GPM of water at 90 PSI, how do I calculate the flow rate at 30 PSI and what rating I would need to purchase to achieve 1.8 GPM at 30 PSI? Below added to give some context, ...
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Stokes Number (characteristic length)

I am working with a high speed flow that is non-stokesian, but that isn't the issue. There are correction factors for that. I am attempting to figure out what value to use for the "characteristic ...
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40 views

Do throttling devices need valves?

Why is it that a throttling device always has a valve leading to it? If in a closed system loop, a cooled gas exists right before the throttling device, shouldn't the sudden decrease in cross-...
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94 views

How does steam in almost vacuum condense at 35 Celsius?

I read about absorption chillers and found out that the water is evaporated/boiled off at the generator. Water boils over at about 3.7 Celsius in the near-vacuum conditions in the generator. Now the ...
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Absorption chillers: can they achieve temperatures below zero Celsius?

If I understand correctly (history shows I probably don't), then the only reason why the absorption chiller evaporators are restricted (I hope that's the right word) to extract just enough heat so the ...
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46 views

Which kind of paper has highest absorption speed?

I am experimenting to analyse the liquid wicking(radial) behaviour of various liquids. I have performed initial studies and experiments on household paper towels but they tend to deform and stick to ...
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47 views

What are the benefits of reducing valve duration in an engine?

From my understanding this would be beneficial if you've taken a stock engine and put a smaller, more restrictive air intake on it. It would also be done to create more low end torque which shifts the ...
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Will high velocity air directed underneath a half-toroid shaped Coanda saucer by a centrifugal impeller create a lifting force?

I would like to know if a lifting force will be created by the Coanda effect from high velocity air that is directed underneath a half-toroid shaped saucer by a centrifugal impeller. I am seeking an ...
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28 views

Symbol for background shear

Can someone please help me with the symbol for background shear? To give you a bit of context, I am referring to background shear as in the following sentence taken from Hussian et al.: Vorticity ...
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1answer
42 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 ...
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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[]=...
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Selecting a water pump for low flow and 1 Bar pressure

I am designing a small automatic drip irrigation system. There will be about 10-15 drippers. Flow through the system will be about 1 l/minute, but this may change if expanding or reducing the system. ...
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Fluid dynamics through tee wye bend

I'm designing a small system where typically a ball valve is used to divert water through a heater when desired. I've noticed the ball valves designed for this situation result in a hard 90 degree ...
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How to use excel spreadsheet formulas to find optimal camshaft profile [closed]

I have a 600cc 4 cylinder Honda engine that my race car team uses. The rules of the race mandate that we install an intake that is substantially smaller than the stock factory intake size to limit ...
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Why is it more convenient to express stress tensor in Material rather than Spatial coordinates?

I was reading chapter introduction about Stress and the author wrote the following about stress tensors: "Since the current configuration of many problems, especially those involving solids, is ...

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