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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21 views

What is the aim of analyzing a tidal(or wind) turine's flow field besides prediction of efficiency and load?

I am studying fluid structure interaction of tidal turbine in my PhD thesis. In my understanding, the aim of CFD analysis for a single turbine is to predict the efficiency and calculate the load [1], ...
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17 views

Testing of water filtration device (and membranes removal characteristics)

I am doing my final year project as an undergraduate and am designing a brackish water filtration device that uses nanofiltration membranes. I wanted to know if there is any suggestions on how I could ...
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2answers
33 views

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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5answers
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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
30 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
68 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
31 views

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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0answers
37 views

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
66 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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2answers
78 views

Why is conservation of mass holds on filling balloon with gas?

Given a ballon and only one inlet, where some gas enters at a constant rate and the control volume of the balloon changes with time, why does conservation of mass hold? To give some background, this ...
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1answer
24 views

Will an electric water pump has slower flow if it must pump through a longer tube?

I am planning a series of ponds, where the first pond (near the source of electricity) has the highest water level, the water flows to the second, lower pond, via a small water fall, and to a third, ...
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1answer
59 views

hydraulic Motor/pump minimum speed

I have seen in many data sheets of Hydraulic Gear motor a spec called : "Minimum Speed = 450 RPM" ( 450 is an example) here is a capture from the linked datasheet below : In your experience ...
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28 views

Ducted fan thrust in confined space

I would greatly appreciate any insight into this. I'd like to place a ducted fan inside of a box with the bottom cut out. The fan is attached to the sides of the box by support rods. The ducted fan ...
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1answer
28 views

Can I calculate the amount (mol or mass) of water in a gas, in a heat exchanger, if I know the partial pressure of the water?

Is it possible to calculate the amount of water (mol, mass...) in a gas, in a heat exchanger, if I know the partial pressure of the water? The stream through the tubes is mainly benzene and ...
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1answer
41 views

Determine the length of the tube

I need to determine the size of the tube having the flow rate of the liquid (water) which is 5 ml/min and assuming the diameter of the tube is 4mm. How can i determine the size of the tube that takes ...
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2answers
26 views

How do stators in axial compressors work?

How do the stators in axial compressors convert kinetic energy to pressure? Is this equivalent to a water hammer?
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1answer
44 views

Help with Mass Flow Rate

I'm a beginner in chemical engineering so apologies in advance if this question is very basic! The Problem You are required to measure the mass and volumetric flow rate of a slurry stream. The slurry ...
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1answer
26 views

Stagnation,static and dynamic pressures

Please can someone help out with the actual concept of stagnation,static and dynamic pressures . I have learnt all that stagnation pressure is when velocity of flow is 0 when isentropically stopped ...
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0answers
18 views

Can you channel more air into a nozzle by creating a vortex inside of it?

There are designs for ducting in wind turbines to channel a wider cross section of wind into the rotor area. This is unpractical for structural and economical reasons but does actually increase power ...
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0answers
27 views

Pressure difference/drop(or loss?) in a Laminar pipe flow

Consider a "pressure-driven" flow ( inlet $P_1$ and outlet $P_2$ pressures "imposed" by an engineer) in a pipe of some length. Under a steady-flow, fully developed region : My understanding: For "...
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1answer
26 views

Boundary layer momentum equation

How does the author get that formula(d alpha formula) using the momentum equation . The book here is Mechanics and thermodynamics of propulsion by Philip Hill and Carl Peterson.
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1answer
56 views

How to calculate flowrate of water through a crosssection of pipe?

Assume we have a pipe with a diameter of 10mm. Water is flowing through that pipe and we know that the water pressure at the 'open' end of the pipe is 2 atm. How would one go about calculating the ...
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0answers
16 views

Air flow at the outlet of a reactor

I wish to calculate the air flow in cubic meters per second of a system that is not exactly a jet engine, but seems close to it, mathematically speaking. The data available to me is the following : ...
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2answers
37 views

Can you help me to source a screw thread G1 3/4 inch to anything to fit in my stainless steel heat exchanger?

Last year I bought s heat exchanger for my above ground 12 foot paddling pool. I also bought a pair of 'gee' one and three quarter thread pva plastic adaptors to push in 50mm plain blank tapered holes....
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23 views

Superimposing a Vector Field onto a Toroid in Matlab

I am a systems and control PhD student in Aerospace Engineering. Currently, I am trying to create a wind shear model of a toroidal thermal "bubble" in Matlab similar to the one in this paper (shown ...
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2answers
34 views

How to design internal wall separation in the PVC tube to use it as a water tanker

I am working on design of the column which contains the water tanker and the pump + electronics at the bottom. I have tried different solutions and they failed. I would like to know your advice on ...
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1answer
8 views

What is the convective acceleration?

I want to gain a better understanding of the convective acceleration that occurs for instance in Navier. Why, in a permanent flow, there can still be acceleration? Thank you
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1answer
37 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 ...
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2answers
57 views

What is the easiest way to regulate the speed of a falling object?

I want to design a system that allows a 1kg metal brick to fall under gravity at variable speeds. The brick initial position is 20cm above a flat table. I want to have control on the duration (to ...
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1answer
29 views

Relation between Inlet and Outlet mass flow rate for a turbocharger?

For the compressor maps for automotive turbochargers, the Corrected mass flow rate (at inlet) is given as abscissa. However, I wish to know the mass flow rate at the outlet. What is the relation in ...
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2answers
49 views

How to calculate heat and mass transfer rates from an enclosed box?

I'd like to know if it's possible to calculate the heat and mass transfer rates from a small volume to the environment. Let's assume there is a box with a small opening at the top. The air inside the ...
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2answers
61 views

Regarding design of a compressed air delivery system based on a screw air compressor

I want to select a screw compressor for my application wherein I need a pressure of about 18 psig, and 300 cfm at the aforementioned pressure. The compressors I'm finding suitable for the system have ...
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1answer
22 views

Ideal Exhaust velocity of a rocket nozzle

In a youtube video, they defined exit exhaust velocity of a rocket nozzle as $$v_2 = \sqrt{\dfrac{2k}{k - 1}RT_1 \left[1 - \left(\dfrac{p_2}{p_1}\right)^{(k - 1) / k}\right]}$$ How can I derive this ...
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13 views

Fitting a gaussian shaped nozzle into check valve piston?

So, for my downhole hydraulic internal cutter tool, I have the following parts: Top sub, body, piston, nozzle, O-rings, knife pins, knives and a bottom sub. I am trying to use a gaussian shaped ...
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0answers
28 views

How do I calculate Pressure drop across relief valve and then force on piston?

So, I'm designing a basic downhole hydraulic tool cutter of an OD = 5 1/2 in., and my tool contains a relief valve and a piston. I am trying to calculate pressure drop across the relief valve so that ...
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2answers
41 views

How far can we compress air manually?

I am not sure if such devices even exist, but I'm sure we can improvise. A device in which we could (manually) turn a shaft, screw a screw, or hammer an air-tight follower into a strong walled ...
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19 views

What are the hypersonic Normal shock relationships?

I am learning about hypersonic flow now and there seems to be a lot of discussion about the oblique shock relationships as the Mach tends to be very large. I was wondering what happens to the normal ...
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0answers
16 views

Visualising why divergence of vorticity is 0

I'm new to fluid mechanics and preparing myself for university next year and I'm reading up on vorticity and circulation at the moment. I understand the maths behind why the divergence of vorticity ...
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1answer
37 views

Why does higher concentration of electonic components decrease the airflow requirement for cooling a PC system?

This source describes in detail a formula used to calculate the airflow requirement in order to cool a computer system. $$Q = \dfrac{P_{loss}}{c_p \cdot \rho \cdot \Delta T}\cdot k$$ Clearly, the ...
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1answer
26 views

At what efficiency does a fan cool a PC case?

A PC case is basically a rectangular pathaway for air to flow through but at the places where the air enters and exits there are solid plastic or metal panels commonly with meshes and little holes. ...
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1answer
20 views

How does fan airflow relate to its RPM setting?

A fan can run at 600 - 2000 RPM, at 2000 RPM it has 50 m3/h airflow. 0% = 0 RPM 100% = 2000 RPM At 50% = 1000 RPM is the airflow halved to 25 m3/h?
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2answers
34 views

Will an empty spray can maintain a vacuum?

If I were to remove all the air from a canister of WD40 so that it was a vacuum inside, and reinforced the walls so that it won't collapse in from atmospheric pressure, what would happen when I pull ...
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2answers
37 views

Divide Flow and Maintain Pressure

Im in the process of building an espresso machine from readily available parts. I have a solenoid pump that supplies pressurized hot water to the coffee grounds. I want to be able to tune the pressure ...
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1answer
43 views

Archimedes Principle Question

A Spherical buoy has a diameter of 2m and weighs 3kN. It is designed to be used in a variety or circumstances by it being floated in water and anchored to the floor with a chain. Draw the free body ...
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1answer
49 views

How can I calculate the airflow needed for a fan to cool a system?

The airflow needed for a system to sustain itself at 80°C with 25°C ambient temperature can be calculated with this formula: ...
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2answers
38 views

How do you find the resultant hydrostatic force on a curved surface which is not exactly semicircle

Assuming this is a pressurized chamber with hydro-static force acting on a semi circle stuck in a surface: To find the resultant force, I would first divide the semicircle into half. Pressure on ...
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2answers
36 views

In marker pens, why does the ink travel to the nib?

This question is specifically for felt tip pens and marker pens that contain a felt inner tube. The parts of the pen are: - the body case - the felt nib - the felt inner tube I do not understand is ...
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1answer
42 views

Airsoft BB Funnel Design - Electric funnel jam solution?

I'm working on a design to feed Airsoft BB's through a funnel. A simple gravity fed system (ie. I don't want to force them out at speed) but every now and again the BB's get jammed at the end of the ...
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1answer
50 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/...
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2answers
328 views

Why Nusselt number for laminar flow in a pipe is independent of reynolds number

I understand that for fully developed flow inside a tube (with constant properties), Nusselt number doesn’t change in axial direction but it is surprising that it is also independent of Reynolds ...

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