# 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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31 views

### Vorticity vs angular velocity

In fluid mechanics, I got confused by the two terminologies, as both seem mathematically and physically similar. Vorticity and the angular velocity in the concept of fluid are the measure of the ...
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### How to calculate nozzle diameters for liquid mixing?

I need to build static mixer for 2 liquids. The liquids should flow from 2 different containers into common container because of vacuum force applied as shown on the picture. The liquids can be be ...
39 views

### Technical names for microturbine designs

When talking about microturbines, I would call a "usual design" a centrifugal pump and a centrifugal turbine facing away from each other and on the same shaft. In contrast to such "...
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### Max diameter of a water pipe acting like a straw

I have a pipe (PE) filled with water, one end of which is raised up, the other is lowered down and closed with a valve. In the middle, the pipe has a "sag", the level of which is slightly ...
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38 views

### Pressure gauge on flow test pipe reading zero, why?

I'm trying to determine the cv values for water of a collection of 90-degree 4-inch elbow valves, and one of the things I need to determine this for a particular flow rate is the input and output ...
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22 views

### How Can I Seal a Sensor into a Cylindrical Tank?

I am trying to seal a dissolved CO2 sensor (From Oxyguard) and a dissolved O2 sensor into a cylindrical tank with a PVC cap. I have a few constraints. The tank will need to be pressurized so I need to ...
1 vote
30 views

### Hydraulic eng. problem

I need to solve this problem for a university course and I’m not sure how to. I’d really appreciate any help. The question is translated to English so I hope it still makes sense. I have a drawing to ...
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### "Vented loop" in fuel reservoir overflow line

I came across some diesel reservoirs in Brussels, Belgium, that appear to have overflow lines with a vented siphon design, see photo below. What's the purpose of this design? I assume the vent is to ...
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### Boundary Layer Growth for Compressible turbulent flow

I intend to use the flat plate analogy to compare results that ive obtained via matlab and see if they match up, and am looking particularly at compressible, turbulent flow. I noticed that the Blasius ...
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1 vote
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### Can supersonic flow be achieved without converging diverging nozzle?

Can supersonic flow be achieved without the presence of a converging diverging nozzle if sufficient pressure difference is available? https://www.tomshardware.com/desktops/pc-building/an-ordinary-...
23 views

### Finding Static Conditions from Total conditions

I am trying to create a code which determines the static properties of a flow given the total (stagnation) conditions, plus an area and mass flow rate. Since the velocity and as an extension, the mach ...
40 views

### Why does subsonic flow decelerate in diverging nozzle and supersonic flow accelerate in a diverging nozzle?

-Why does the pressure decrease in the converging section for subsonic speeds and the speed increases? -Why does the pressure increase in the diverging section for subsonic speeds and the speed ...
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### How does this water canon function?

While idly watching shorts, I came across this one. And after watching it a hundred times, I still don't understand how the water canon functions. I mean, where is the pressure coming from? The design ...
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### How does one calculate the aerodynamic pressure on a spacecraft during Max Q?

Just as lift - off of a spacecraft commences, that spacecraft undergoes aerodynamic pressure. After a certain point, the spacecraft reaches Max Q or maximum aerodynamic pressure. I do know that Max Q ...
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### Palm tree misting system to kill beetle pest "rhino beetle"

In Hawaii we are having a huge issue with this pest called a "rhino beetle" These beetles eat the heart of palms, eventually killing the palm completely. Soon Hawaii will have little or no ...
27 views

### Finding Pipe Diameter from Flow Characteristics

I'm trying to find an equation that will give me a required pipe diameter, the variables I have are the following: Fluid characteristics (argon) Volume flow rate at exit Pressure at input Pipe length ...
1 vote
90 views

### Water Hammer is damaging the pump!

I live on a small farm with my wife. We drink rain water from a rainwater tank. It's a small, simple system. However, we have water hammer occurring between the supply water tank (Supply Tank) and a ...
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1 vote
91 views

### Can air velocity be supersonic in a straight pipe?

Consider a sufficiently large reservoir of compressed air at a pressure of $7 \text{ bar}$ (abs.). A tapping of $25 \text{mm}$ diameter of pipe length $1 \text { m}$. The pipe is open to the ...
33 views

### Why there is no cavitation in water towers?

Water towers seem very high, some are more than 10 meters. With such high water towers, is cavitation possible in the pipe supplying water from large tank to the delivery pipe on the ground? Is the ...
33 views

### Difficulty in understanding the trigonometry in applying the momentum equation for a stream tube

As far as I can understand the sum of the applied forces is the component of the weight of the fluid in the s direction and pressure forces. Looking at the diagram ...
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### Flow in vent of a pipe

I have a horizontal pipe of diameter 2000mm (uniform cross section), the pressure of gas flowing in the pipe is 1.2bar and the flow velocity is 15m/sec. there is a 100mm diameter vertical vent ...
45 views

### Temperature profile in a pipe flow with Matlab pdepe solver

I’m currently trying to solve the heat equation for the Ohmic heating of a pipe flow using the MATLAB pdepe solver. The problem is described in the following paper: https://doi.org/10.4236/ojmsi.2021....
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### Index notation for the generalized form of the velocity field dependance on shear and rotation

Good day guys, I was studying fluid dynamics and came across the following equations (shown in the image): When we have both shear and and rotation, they each contribute to the change in velocity ...
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51 views

### are ducted fans better than turbines generating vaccum?

Basically I want to make a trap that sucks mosquitoes into a screen container for future studies, to do this I need to generate a vacuum and I need to choose whether to use a ducted fan (simpler) or ...
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### Momentum Diffusivity without Mass Diffusion in Liquids

I have been reading about the differences between momentum and mass diffusivity. I understand that mass diffusion occurs because of the "random walk" of individual molecules which over time ...
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### Calculating the convection coefficient of a green roof

as part of a course I have to calculate heat transfer through a green roof. I'm using Python to carry out an assessment over twenty years. The data I have are irradiance, wind speed, air temperature, ...
1 vote
40 views

### What is the flow rate at pressure x when given these pressure drops?

I was given a work problem. There is a water pipe that has a leak. The leak appear very minor. Some staff decided to try and measure the leak after shutting the water off at both ends of the pipe. ...
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### Pessure required for pumping seawater through pipe with inlet at a depth below sea level

I need to calculate the head capacity required at the pump, to pump sea water from a depth of 100m below sea level i.e. inlet is at 100m below sea level, the recieving end is at 5m above sea level. ...
21 views

### Is there a dimensionless number for wave guide width and frequency vs turn radius?

It seems like there should be a dimensionless number for wave guide width and frequency vs turn radius, but I have not been able to locate it or understand the proper application of one I am ...
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1 vote
23 views

### What are the boundary condition to simulate flow through vent mast?

Dear all, I am currently working on modeling compressible flows that occur when hydrogen needs to be evacuated (for purging, in case of fire, etc.). I am endeavoring to determine the appropriate ...
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### I want to find the energy capture from a submerged "waterwheel" type turbine with converging plating of 21 degree to form a ducted funnel

The inlet end would be 1.545 m wide x 1.170. The outlet to the flat turbine blades would be 0.806 m wide x 0.67 m and length would be 1.043.5 m. There are 8 x turbine plates of 0.415 m long x 0.67 ...
56 views

### Spike in frequency domain in a dataset recorded using electromagnetic flow meter

I am trying to measure the water velocity of a stream along a channel using an electromagnetic flow meter at a specific location and depth. When I converted the data into frequency domain as power ...
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### Designing a tea strainer: Plastic vs stainless steel

Some time ago, I finished designing a tea strainer and I had a prototype printed from a certain heat resistant type of plastic (https://xometry.pro/de/materialien/standard-heat-resistant-pc-artig/) ...
1 vote
47 views

### Formed Suction Intake - What is the purpose of splitting it?

Some FSI's appear to be split down the middle. Others appear to not have this split. What purpose does this component serve? Is this component ever serving the purpose of a structural support?
1 vote
27 views

### Seeking Manufacturing Advice: Low-Dose Powder Dosing Device

Hi everyone, I'm working on a project that requires a device to dispense a very small amount of powder (around 1 gram per second) in short bursts. Ideally, the device would "sneeze" the ...
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38 views

### How do you calculate float speed?

My question is about fluid mechanics Based on and I understood correctly, buoyancy after release in still water becomes a constant velocity and based on my understanding correctly and the force acting ...
1 vote
93 views

### Dixon/Hall's "Fluid Mechanics and Thermodynamics of Turbomachinery" full of errors?

Note: This is no homework, but self-study. I have a thermodynamics and fluid mechanics background and am trying to work through this book in order to get better understanding of turbomachines (...
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### Difference between pressure drop and vacuum

This is a question that has been haunting me my entire career. The pressure loss caused by friction is not the same as the pressure "loss" caused by vacuum, right? I mean, if I have a gas ...
39 views

### Can changing the topology of surface water initially hits change how much it splashes?

I am designing a crude funnel to feed into a portable dishwasher. I was not allowed to attach to water lines so I am stuck with pouring 1.5 large pitchers of water into it. I am designing a funnel to ...
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1 vote
91 views

### Is it possible to use two sets of stator blades after each set of rotor blades in an axial compressor?

I am currently designing an axial air compressor for a project, and I require the stator blades to reduce the velocity from 50m/s to 2.5 m/s in each stage of the stator. This requires a ratio of the ...
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75 views

### Quantitative Risk Assessment Of Onshore Crude Oil Pipelines

I am currently working on a project that requires a quantitative risk assessment of a potential release (analysis of frequency and consequences) onshore pipelines transporting crude oil (underground). ...
1 vote
49 views

### Why do wing-tip vortices cause an induced angle of attack upstream?

My question is the following. Wing-tip vortices induce a downward flow on the root side of the wing. So, if this induction happens at the wing, and these vortices are then shed downstream, why is ...
52 views

### Why do trailing edge flaps increase the CL,max of a wing?

I was wondering why do trailing edge flaps increase the lift co-efficient for a given angle of attack. I am guessing it has something to do with delayed flow separation, but this is quite unintuitive, ...
27 views

### Restrictor Nozzle Back Pressure

Using a flow restriction to create backpressure. The back pressure is very important as it is used to drive a piston. What nozzle/flow restrictor shape will create the highest pressure drop/back ...
1 vote
103 views

### How Calculate Stored Potential Energy of Pressurized Water

This is a real-life question. I work in construction. Several engineers involved have come up with different answers. Which one is correct, and why? We are developing the plan to hydrotest a tunnel. ...
1 vote
39 views

### Why is electroosmotic flow plug-like?

Hey, I am studying for a microfluidic exam and can't wrap my head around electro osmotic flow: why is the velocity profile plug-like? The fluid motion in the bulk phase away from the double layer is ...
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### Trying to gain a deeper understanding of what a system curve (pressure vs flow) actually represents

I'm trying to make sense of what a system curve is, and I have three different conceptions in mind. Note: I don't have an engineering background, and these are relatively new concepts to me, so I may ...
69 views

### Theory of rotationally symmetric air cushion vehicle

I am trying to develop a theory for this situation: A small blown-up balloon is attached to the center of a compact disc; you let it float as the balloon discharges. Simplifying assumptions: ...
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