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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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Liquid phase gas flow through valve

I have been trying to figure out how to calculate the required dimensions for liquid phase gas through a solenoid valve. Many companies (Swagelok, Bürkert, Asco) provide "Flow coefficient calculators" ...
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2answers
33 views

Sea waves: Having trouble visualizing the difference between group celerity and celerity

What I know, if I'm not mistaken, is that group celerity is the speed at which the energy is transferred and celerity is the speed of the waves themselves. Since sea waves basically transfer energy ...
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3answers
64 views

How does an expansion tank work?

I know that a hydronic system forms a closed loop. When the boiler is turned on, the water temperature will increase and expand. Since this system forms a closed loop, there is no volume for the hot ...
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49 views

What does the following statement of Bernoulli's equation mean?

Bernoulli's equation can be applied between any two points on a stream line for a rotational flow field. Can anyone explain me the above statement?
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20 views

Is there any real life application of potential function and stream function in fluid mechanics?

Theoretically, I can grab the meaning of potential function and stream function. But I don't see how this can be used in real life. How are those concepts used in real life?
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18 views

Where to put the booster pump at customer substation in a district heating system?

In a district heating system, one of the houses in the distribution net is not getting the desired heat into their house. This is because the pipes of this customer which connects them to the ...
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1answer
42 views

Which way should I build stairs into a creek?

I have a little creek in my back yard. It's slow moving and safe (as safe as a slow moving creek can be.) I'd like to build a little set of stone steps into the creek and am not sure of the best ...
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0answers
29 views

Time to empty a pressurize oxygen tank through a regulator

Time to empty a pressurize oxygen tank through a regulator. The tank contain 12oz of oxygene at 3000psi (room temp.) The regulator is set to 120psi. The exit pipe is a 14inch pipe with 2mm inner ...
3
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1answer
44 views

Ideal funnel design for powders

I'm designing a funnel/bottle for a powder. My goal is to have all of the bottle's powder contents come out when inverted. However, the powder has a tendency to stick to itself (like flour or brown ...
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0answers
23 views

Flow rate at the vent exit

I am working on a vent. The vent is attached to a box and is designed to extract air out of the box using the venturi effect. Air is made to flow over the vent which creates a significant pressure ...
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1answer
93 views

Why using average pressure in calculations gives the most accurate results?

In the saga of trying to answer the question that came into my mind while studying the basic concepts of Fluid Mechanics, "Why textbooks use geometric center to calculate hydrostatic pressure when ...
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2answers
116 views

Why textbooks use geometric center/centerline of the pipe when calculating/measuring pressure?

Studying Fluid Mechanics, I started to notice that almost every textbook/website uses a specific point to make calculations about the pressure in a liquid at a given depth (hydrostatic pressure): the ...
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1answer
29 views

Is there an ideal propeller shape?

Are there theories that assert about the ideal shape (i.e., ignoring structural constraints) of a propeller? Just looking at the shapes that emerge in practice, it appears that both the fluid speed ...
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1answer
37 views

pressure loss in a T fitting

For weeks I have been searching internet , but still unable to find answer , so here it goes: I have to calculate pressure losses in heating circuit , and am stuck at calculating losses in T fittings. ...
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0answers
33 views

hot wire anemometry

Hot wire anemometry can be used to measure the temperature of a wire in fluid flow. The voltage fluctuation across the wire is used in conjunction with an energy balance on the wire to obtain the ...
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13 views

hydro aspirator design parameters

I am looking for design equations, or reference designs in order to maximize the vacuum created by an hydro aspirator such as the one pictured here. https://en.wikipedia.org/wiki/Aspirator_(pump) ...
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1answer
23 views

Solving 1D Unsteady Homentropic Flow using Method of Characteristics

I am looking to solve the 1D Unsteady Homentropic Flow equations using the Method of Characteristics (MOC). I am using Zucrow and Hoffman's Gas Dynamics Volume 1 as a reference and I am currently ...
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0answers
10 views

Horizontal tip extensions and C-wing design for stability of tailless drone

I am a robotics student and new to aeronautics. My task for a project is to build a flying wing drone with limited wingspan (<1m), 25cm chord at wing root, total load of 2.5kg (1.5kg empty) and ...
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0answers
23 views

Positive displacement pumps working in parralel

I am using two +ve displacement pumps in a system. One as Feeder pump with 3cc/rev with feeder tank and other 1.2cc/rev as metering pump. There is a small tank (accumulator) in between before metering ...
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0answers
38 views

Determining the Steady Discharge Between Two Reservoirs

A uniform pipeline, $5km$ in length, $100mm$ in diameter and with a roughness size of $0.03mm$, conveys water between two reservoirs. The difference in water level between the reservoirs is $...
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1answer
34 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 ...
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1answer
38 views

A sphere of radius R, made from material of specific gravity, SG is submerged in a tank of water

... The sphere is placed over a hole, of radius a, in the tank bottom. Develop a general expression for the range of specific gravities for which the sphere will float to the surface. I've attached ...
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0answers
20 views

Water distribution

Dear all, I have a problem regarding water distribution. The aim is to get all the water distribute evenly with same speed, volume and pressure with approximately 20 nozzle. The problem is water ...
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0answers
23 views

Uniform steady flow towards an immersed sphere

A sphere is immersed in an infinite fluid of 1D, steady flow. The oncoming flow velocity is $U_0$. the flow field is given on the AC line as:$$\overline{V}=\mathbf{i}u(x,t)=\mathbf{i}U_0(1+\frac{R^3}{...
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1answer
34 views

Pressure rise in horizontal pipe

What causes the pressure change in a horizontal pipe with no energy input. Is it the head loss? If so, how?
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0answers
21 views

Flow rate for a domestic water flush

I have a 8" pipe tied into a 16" water main to be flushed. Specification requires a specific flow rate. Pressure is 85 Psi. and discharge is 4" and pipe is horizontal. Too much flow to normal ...
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2answers
48 views

What pressure to take in surface tension question?

Pressure inside a water droplet is $0.32 N/cm^2$ if surface tension of liquid is $0.095 N/m$. We have to find the radius of the bubble since it's a water droplet the formula used is $$P_i-P_o=\frac{...
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2answers
32 views

Force applied by fan under inviscid & incompressible flow

I have a wind tunnel (subsonic flow of air) which consists of a fan inside (and ahead of) a long cylinder of cross-sectional area of $A_e$, followed by a diffuser of $A_o$ c.s. area ($A_o>A_e$). ...
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1answer
70 views

Difference in Diameter calculation using Solidworks and manually

When I try to create a flat form of a archimedes screw using Solidworks it gives me a diameter different from what is calculated manually basically using a Pythagoras Theorem. Can anyone explain the ...
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1answer
27 views

Calculating typical floor fan efficiency or dP? (Spec sheet too good to be true?)

Looking to purchase a fan with high velocity. Trying to make solid data driven decision based on specs. Found that most fan's of the 20" diameter variety are around 3000 CFM; however found one that ...
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2answers
45 views

Polyurethane mix-on-the-spot system

3d printing is a slow process and for my solution I need fast printing. So I print with no infill and I fill inside with a two part, 10 min drying polyurethane resin. I mix them in a disposable cup ...
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0answers
30 views

Tempreture distribution in a furnace

I am simulating a furnace as follows: Is it possible to capture temperature distribution in this furnace without designing intake fan? Which kind of boundary conditions can replace with intake fan? ...
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0answers
25 views

Stream function in fluid mechanics

The stream function Ψ for a steady flow field can be defined as: ρU = $\nabla \times$ Ψ. Where, $U = velocity$, $ρ = density.$ Now, this Ψ can be in turn represented as: Ψ = χ $\nabla$ ψ. Where, ψ ...
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1answer
35 views

Torque on the curved moving vane

I was reading an article on the impact of jet in vanes. In this article I found that the net torque on the unsymmetrical or radially curved vanes is non zero. But, my question is that, why the torque ...
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2answers
58 views

Calculation for heat transfer rate / cooling capacity for air cooled solid

I have a pipe which is channeling air flow from a compressor with a known mass flow rate and temperature. I can adjust the mass flow rate (power setting) and measure the delta T for the temp of air ...
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0answers
16 views

How do I add multiple materials in Helyx-OS which use OpenFoam for CFD analysis?

I am trying to learn HELYX-OS which is a GUI for OpenFoam. But I cant seem to add more than one material for the system and it is only allowing me to add one material no matter which modal I use.
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2answers
37 views

What should be the density of a compressed gas while measuring the flow rate using Rotameter?

Say we have a required mass flow rate, in order to have equivalent volume flow rate, we need to consider density of the operating fluid (compressible fluid). To measure the volume flow rate in LPM, ...
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1answer
28 views

If I replace a flow orifice with a Coriolis flow meter of the same size do I need to worry about pressure drop with the new Coriolis meter?

I have a 3 inch line with a 1.5 inch flow orifice. If I take out the flow orifice and put in a 1.5 inch coriolis meter will the pressure drop be the same or better with the new coriolis meter than ...
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1answer
52 views

How to solve analytically this equation? [closed]

I need to solve the next equation and to find $x_1$: $$\dfrac{d(x_0x_1)}{dz}=-\beta\dfrac{dx_0}{dz}\dfrac{1}{r-z(r-1)}$$ where $x_0$, $x_1$, $z$ are variables, and $r$, $\beta$ are constants. At ...
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2answers
39 views

Why aren't turbos/turbines controllable pitch?

I am wondering why turbines are not implemented with controllable pitch blades (on the rotor system)? I assume the reason is that the coupling between the stator and rotor systems posed by typical ...
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1answer
36 views

Reduce and compute flow in self designed pen

I am currently designing a simple pen for drawing with different types of liquid varnishes. My current design has a tip at the bottom side of the pen (blue) and a tank at the top side where the ...
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2answers
61 views

How does placement of a pressure gauge in a tank of fluid affect the pressure readings?

This is not a real system but rather something I made up to understand how the placement of pressure gauge in a tank takes its readings. Here’s a diagram of it- The pressure gauge placed in the ...
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1answer
22 views

Why does the water pressure initially drop then stabilize when pressure testing a valve?

Sometimes the dropping goes on so long(10-15 minutes) that the test is thrown out and the valve is opened and filled with water for a longer period of time. Pressure testers claim that it is because ...
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3answers
43 views

Is there any entrance losses in this particular Pipe design?

Let’s say this odd design, the arrow is the direction of water flow (don’t ask why because I’m just curious about it)... I drew this out and just wanted to ask if water were to flow into the pipe ...
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1answer
54 views

Design of a small scale air curtain

I am new to the field, most of the papers I have searched directly conduct CFD simulation but skipped the calculation. I hope to get an estimation by calculations. I am designing a small scale ...
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0answers
26 views

Ansys Fluent: how to change the temperature digit precision in writing to file XY-plot?

I want to write to file data from XY-Plot with temperature depending on the location. In Axis menu I set a max precision (9) for X and Y. However, Fluent writes data like this ...
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4answers
99 views

what's the best shape for inducing condensation?

What would be the best ceiling shape for inducing condensation? I'm guessing it would a curve ︶ or V shape, but those are just guesses. (I don't have any background on thermal physics)
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2answers
82 views

Finding out torque in a viscosimeter

I am solving problems through Fox and McDonald.Here is the problem I tried by finding out the torque due to viscous forces which is $$\tau_1=\mu(2\pi Rh)\frac{R\omega}{a}$$ and the torque due to ...
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0answers
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Does impeller design have a specific cause on how the fluid will flow in a centrifugal pump?

I am a student learning about centrifugal pumps in my studies. I’ve learnt about the 3 different type of flows - axial, radial and mixed. I’ve also learnt about different impeller designs - mainly ...
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1answer
46 views

How can i calculate drag on an Angled area?

I want to calculate drag force at special angle on a sphere . There are some grooves on the sphere and these groove have a special angle on the sphere. In other words, I want to calculate drag force ...