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 views

Air flow optimization in a small opening

I have a 36 x 6 cm opening from where I need to pull fresh air. I need to optimize for air flow as well as noise. I considered using 6 Noctua NF-A6x25 fans which would give me a total of 175,2 m3/h at ...
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1answer
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How could an absorbent material be emptied?

I have been thinking about this for quite some time: Given a foam or other absorbent material saturated with a solvent, how could you draw all the solvent to the top of the foam (basically how could ...
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Navier-Stokes with non-newtonian fluids

So I've got a problem here in fluids. It's driving me insane but I know I'm missing something simple. Up until now we've worked with Newtonian fluids resulting in the "normal" NS equations ...
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can anyone analyze this graph [closed]

Analyze this graph : Depth Deficit Ratio (Water Management Resources) Civil Engineering
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Blade efficiency of a franscis turbine

The blade efficiency of a turbine is defined as the ratio of the power extracted from the fluid by the rotor to the power available at the inlet of the rotor. The power available at the inlet of the ...
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2answers
37 views

Sunlight-powered device set to change world: will it work? [closed]

Vast areas of desert sand are being shone on upon by the sun. Now that's some ENERGY! Using this proposed apparatus: Sunlight over large area is concentrated on steam chamber, where water turns into ...
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How to Derive the Differential Form of the Contintuity Equation

The book "Gas Turbine Engineering Handbook" by Boyce, on p. 117 states, the continuity equation, $ \dot m = \rho A V $, has as its differential form, $ 0 = \frac{d\rho}{\rho} + \frac{dA}{A} ...
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Understanding Stagnation Pressure Head in non-compressible fluids

Does the stagnation pressure head in a pitot tube allow for the calculation of dynamic head at a point in the tube, given that the static pressure head at the point is known? For example in the ...
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Explain pressures created by fluid flow through small orifices

So my question is in relation to fluid flow and pressure. In my pictures below you can see that i have two similar situations. Fluid flows in from a large reservoir at a constant rate through a ...
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2answers
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Can you shape a buoyant object stuck to the bottom of a body of water such that it floats?

I understand that an object, say a closed plastic cube full of air, stuck to the bottom of an aquarium with a smooth glass bottom will not float if you firmly place it such that no water can get ...
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Is there a valve design or system that can do this?

I am trying to come up with a way to bleed air from a tube to avoid air (gas) from reaching the other end of the tube. Is there a way to do this automatically? It must be able to work in all ...
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1answer
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How to make a 500+ psi water gun staff

I would like to create a life size lego Bionicle Aqua axe(gali nuva Type or gali master of water Type). The problem is unlike The trident in this video: https://m.youtube.com/watch?v=NK6MWt7vpVE&t=...
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What is the use of streamlines in Fluid Mechanics when velocity fields seem sufficient?

So, streamlines are a family of curves which, for every instant in time, are the velocity field envelops. And in general, envelopes of a vector field are the curves whose tangent vector at each point ...
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Simplifying the soda gun mechanism

I'm looking to design a push button mechanism similar to the soda gun where water is forced to pass through a single passage based on which button has been pressed. What are the different approaches I ...
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2answers
44 views

How do I connect multiple water-filled syringes?

I'm trying to connect 4 separate syringes containing water and we need water-tight tubing to prevent water from leaking out of the system. The water would theoretically need to be pushed out of one ...
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1answer
51 views

Does the aerodynamic force qualify as a viscous damping force in the Mechanical Harmonic Oscillator

When reading about a harmonic oscillator, the most common form of damping is proportional to the velocity. $$F_D = c \;\dot{x}$$ Without giving much thought to viscous damping, one example I always ...
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1answer
78 views

Head loss for T junction diverging water pipes

I am writing to ask for help with a T-junction pipe problem. Attached picture shows the pipe configuration. The schematic shows a large pipe with ID 16.5mm and smaller 4mm ID tubes connected to it. ...
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2answers
66 views

Turbulent boundary layer development in channel flow

I'm currently working on my Bachelor's thesis about the numerical simulation of a turbulent air flow through a rectangular channel. As part of that I'd like to compare my results to empirical ...
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2answers
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Why do all quantities used in the formulation of a physical law must be coordinate-invariant?

So I have just started reading the book "Introduction to Continuum Mechanics_third edition" written by W. Michael Lai, David Rubin, and Erhard Krempl. At the end of the book's introduction, ...
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Why don't engineers put tesla valves in the airboxes of carbureted internal combustion engines?

Before I ask the full question, I want to quickly cover two common issues that come up in high performance engine design. When intake valves close in an engine a small shockwave moves backwards ...
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Why funnelling air in order to increase the velocity is a bad idea when generating power

Disclaimer: I’m not trying to violate the conservation of energy here; I know that’s impossible for us mortals. I think I’m either wrong or not considering something, I just want someone to point it ...
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Why aircraft refrigeration uses a centrifugal compressor in place of reciprocating compressor?

Why aircraft refrigeration uses a centrifugal compressor in place of reciprocating compressor and a gas turbine in place of reciprocating expander?
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25 views

Sutherland's law for other gasses

Sutherland's Law seems to be a fairly well-accepted relationship between dynamic viscosity and temperature and was originally created to work for ideal gases, though it is often extended to be used ...
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Advice wanted on time to digital converters for speed of sound in fluids

I'm using the speed of sound to analyze the composition of aqueous solutions with sound velocities between around 1000 and 1400 meters per second. It's a process control application with continuous ...
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1answer
47 views

Determining the final surface temperature and final gas temperature flow through a tube in a room

I am trying to calculate the final temperatures as stated above. There is hot gas flowing through a tube that is insulated and inside of a room (no wind). I will try to walk you through my thought ...
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1answer
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Determine in and out momentum in shell momentum balance [closed]

How to decide what is in momentum and what is out momentum in using shell momentum balance? My main motive is to understand why at 25:26 in the balance equation at https://www.youtube.com/watch?v=...
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1answer
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Hydraulic lift connected to two pistons

I just finished a problem, and got the correct answer, however I am confused on one of the mathematical operations that must be performed in order to get the correct answer. The problem is as reads: ...
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2answers
36 views

Stop Spa-to-Pool Siphoning Thru Spa Pump

I have a partially above ground Spa and an in-ground pool. When the spa is filled to spillover with pumps off, water siphons through the spa pump and into the pool until the spa water level drops ...
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1answer
36 views

Slow Driving an Air Compressor

Do off-the-shelf air compressors have minimum driving speeds, below which they cannot build the necessary pressure? Reciprocating compressors and scroll compressors are available—is there a difference ...
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2answers
26 views

Will coefficient of discharge remain same when it is used for measuring either liquid or gas flow rate?

I would like to measure air flow rate. I have a orificemeter but do not know its coeficient of discharge. Will the Cd remain same for both the liquid and gases or it will be different.?
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Archimedes screw pump

i want to know if an Archimedes screw pump is more eficent that a modern screw pump to elevete clean waters 4 meters i saw many modern screw pumps smaller and want to now about the efcency of ths two ...
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3answers
42 views

Separate air from water for water pump in aquarium

I'm using the following setup to pump water out of a space below the gravel (yellow) in my aquarium: The tubes displayed as lines are 12/16mm silicone tubes. The pump is a 300l/h electrical water ...
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1answer
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Fluid Mechanics Question

I am preparing for GATE(Chemical). I need the answer of this question part 2 (question 54) as I am not able to find the mistake in my logic. I have applied the logic here as: Initial energy stored in ...
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1answer
58 views

Throttle vs Choke vs Damper vs Valve?

Throttles, chokes, dampers, and valves all restrict fluid flow. Aside from specific terminology/usage in internal combustion engines, are these really interchangeable terms, or do they have some ...
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1answer
61 views

Would this air amplifier attachment increase a leaf blower's effectiveness?

With the start of the leaf raking/blowing season just a month away, I have been thinking of a way in which I could make my old leaf blower more effective so I can spend less time doing leaf blowing. I ...
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2answers
54 views

How do you maintain a constant pressure in a pipe with multiple outlets?

I've seen in piping and ventilation systems, when they branch off, the continuation of the main trunk gets smaller. Presumably this keeps the pressure (sorta) constant along the whole length of the ...
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2answers
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determine if the flow is laminar or turbulent [closed]

what would be the the type of flow if the water flows through stainless steel channel? would it be a laminar flow or turbulent flow. I assume the adhesive force of water to stainless steel is minimum.
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1answer
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Does filter surface area affect resistance?

I am in the process of designing the enclosure for a small kiosk like project, and intend on having two fans (Noctua NF-A12x25, chosen for their high runtime rating, quietness, as well as other ...
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3answers
348 views

Why is the friction factor in laminar flow independent of pipe roughness?

The Darcy friction factor is defined as: $$f_D =\frac{64}{Re}$$ with $Re$ I mean Reynolds number (global). I was wondering why Darcy in laminaire flow is independent of pipe roughness (wall roughness)?...
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2answers
50 views

incompressible fluid approximation and fluid vs sound velocity

consider the following case: A straight tube, with a constant mass flow rate of water $\dot m_{in}=\dot m_{out}$ , and with a linear power entering in it $\dot Q [\frac W m]$. And the water is the ...
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1answer
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Coefficient of viscosity equation/answer issue

So I feel like my current answers are wrong but I am unsure, i feel like some could be a little high at -223 but I dont have the best experience in the field as this is my first time working with ...
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1answer
43 views

Not too sure how to approach this equation - fluids mechanics

Apologies if anything has been left out. Ok, so there is just 1 equation which I am struggling to understand, I have made an attempt and also written out the full equation in 2 parts, but I dont know ...
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54 views

Axial fan for HVAC with HEPA filters

I have a background in mechanical engineering but HVAC is not my specialization. I am trying to properly size an axial fan to get a determined airflow from a duct. Both inlet and outlet are at ...
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2answers
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Unequal water level in connected containers - Aquarium Sump

I have recently designed and had fabricated the following two sumps for my Aquarium (See image). I have a pump in the right hand container (section 4), and the return is coming back into the left ...
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Can a riverboat tack upriver?

Note: This question originally appeared on the Physics site (see here) and was closed for being off-topic. Whoops! If ships at sea can tack in a zigzaggy pattern by converting backwards force from the ...
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1answer
32 views

How are the conditions after the shock calculated for a shockwave formed on a cone?

How do oblique shockwaves differ from 2D to 3D problems? More specifically, how are the conditions after the shock calculated for a shockwave formed on a cone (e.g. the inlet cone on a ramjet)? I am ...
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1answer
74 views

Fan blower with less airflow in the center

I'm building a ducted fan and I would like it to: have a uniform airflow at the output have good static pressure have a square section output (see figure: air enters the circular edge and exits from ...
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3answers
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How can I keep my soda bottle at atmospheric pressure while dispensing the liquid via a sealed system pump?

I am making a "bar bot" and I am trying to figure out a way to dispense soda without it going flat. I am using a bunch of peristaltic pumps: Which luckily remain sealed at rest. I was ...
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UV radiation simulation in ANSYS

I am setting up a simulation in fluent to estimate the UV radiation dosage of an air stream passing through a cylindrical duct with the UV source in line with its main axis. It is a very simple system,...
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1answer
70 views

Accounting for pressure energy in Euler turbine/pump equation

For all the analysis to find work done by a compressor or work done on a turbine, the book I'm reading (Fundamentals of Turbomachinery by Venkanna B.K) uses the Euler turbine and pump equation, $$W=\...

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