Questions tagged [fluid-mechanics]

Questions relating to fluids at rest (fluid statics) or the forces and effects of fluids in motion (fluid dynamics).

Filter by
Sorted by
Tagged with
0 votes
0 answers
22 views

Navier-Stokes Problem

I've been trying to solve this problem for a while now. I've tried simplifying and finding boundry conditions (such as the no-slip condition), but I can't seem to simplify it enough to make it ...
0 votes
0 answers
25 views

Flow across V-notch

I have an exercise where I have to calculate the flow that passes through a V-notch with the angle <$\theta = 150 ^\circ$> and the head h1. The notch has an upward going slope. (I don't know if ...
  • 7
0 votes
1 answer
29 views

Submerged fraction buoancy force

How can I calculate the height of the submerged part of a partly filled bucket? (The liquid both inside and outside is freshwater). The bucket is trapezoidal such that the volume of the submerged can ...
  • 7
0 votes
0 answers
5 views

Centrifugal pump head-flow prediction with CFD

Given a volute pump casing, the impeller, and RPM how would one obtain a simulated head-flow graph? As for what I have seen in research papers most methods already assume input flowrate / pressure and ...
0 votes
1 answer
37 views

Vertical pipe flow

I want to know the flow through a vertical pipe when a valve in the bottom is opened (a disk is lowered as illustrated in the drawing) I know the heights in the drawing and the diameter of the pipe. ...
  • 7
0 votes
2 answers
48 views

Do curves and bends in an airduct (or airpipe) influence the energy that can be captured from that airflow?

To better explain my question, I've included a schematic below. Let's assume that the water level rises. As the water rises in the wide chamber, it displaces the volume of air and essentially pushes ...
  • 75
0 votes
0 answers
25 views

How to calculate the Knudsen number?

when calculating the Knudsen number: $$ Kn=\frac{\lambda_{mf}}{L} $$ Where $\lambda_{mf}$ is the mean free path of a molecule, and $L$ is the characteristic length. How is the characteristic length ...
0 votes
0 answers
12 views

Does stress have to be isotropic in fluid under static equilibrium?

Does the Cauchy stress tensor under static equilibrium in a fluid HAVE to be isotropic? If so why? I would like to be pointed to rigorous mathematical resources that show this. What physical ...
0 votes
0 answers
20 views

How could Adrian Bejan's 'Constructal Law' be formulated mathematically?

Adrian Bejan is known for having devised a very interesting theory for the hierarchical and aesthetic structure found in nature, from the branching tree shape of river deltas to the tree shape of ...
0 votes
1 answer
32 views

Hydrostatic force acting on a hemispherical impression

Consider vertical wall which contains a hemispherical impression as shown. Water is filled only upto the centre of hemispherical impression, i.e. to a depth of L. It is required to know the horizontal ...
-1 votes
0 answers
12 views

Dimensional Analysis for Fluid Dynamics: Shear Stress Exerted By A Fluid

I'm confused by how the dimensions for a Fluid Dynamics problem make any sense. (Yes this was homework, that I've already completed and submitted, I'm just trying to learn the concept). Anyways, you ...
0 votes
1 answer
38 views

Why air cannot be used as a cooling medium in CO2 refrigeration system?

Can anyone please explain the reason for above question?
0 votes
2 answers
40 views

Solve an Air Conditioning condensate drain problem

While working from home (a 1968 build retrofitted with A/C) here in FL I've noticed that my A/C drain makes a gurgling sound. I've traced the sound to the condensate drain pipe which appears to be in -...
  • 1
0 votes
2 answers
43 views

Can ocean flows after a crashing wave be accumulated in one point to increase the water height of that location?

Here in this image, you can see the water flow onto the beach to a certain distance. After a while, the water retracts back. If I put a V-shaped collector (like a vertical standing open book) facing ...
  • 75
0 votes
3 answers
75 views

How do i calculate, and make sure that the same amount of water comes out from every hole in my pipe?

I need to distribute the water evenly between five holes in my stainless steel pipe. How do i calculate which size the different holes need to be, in order to get the same amount of water out of each ...
  • 1
0 votes
0 answers
38 views

Will any buoyant force act on the block when it settles at the bottom?

Consider a cylindrical container that is filled with water to the rim. Now, an iron block of Volume $V$ is dropped slowly into the container. The volume of the water that spills out will also be $V$, ...
0 votes
1 answer
18 views

Does pressure/temperature drop in a funnel or nozzle with a gas being pumped through it by a fan

So, I was thinking about trying to build some kind of body cooling suit and started looking into the wonderful world of refrigeration systems. I've managed to get myself side-tracked pretty badly ...
0 votes
1 answer
29 views

Heat added per unit mass in a cylindrical pipe

I have a question, which seems simple, but for the life of me I cannot figure out. So, let's say I have a very thin cylinder (consider an interface), between two fluid with different temperatures. The ...
  • 1
0 votes
2 answers
50 views

Can the crest of an ocean wave be increased by directing ocean waves to a center of a curved column?

My question really pertains to improving the oscillating water column device to generate greater electricity. The way the current system works, when a wave with a crest hits the wall, the water inside ...
  • 75
0 votes
2 answers
58 views

Why $\frac{m}{V}$ gives average density when density varies?

This might be a very basic question, and for years I have gone by simply accepting it as a fact. That whenever the density is uniform the formula $\frac{m}{V}$ gives that uniform value of density and ...
0 votes
1 answer
24 views

How does decreasing the cross-sectional width of a channel impact steady flow?

The continuity equation states that for a constant mass flow rate, if the cross sectional area of a channel is decreased, then velocity is increased. What happens if the channel has high walls and is ...
  • 75
0 votes
0 answers
22 views

Effect of air flow speed on thermal time constant

Suppose a simple case : A fan blows air on a rectangular object made of aluminium. If you need to add some dimensions to the object, do not hesitate The air speed is at X m/s and the air is flowing ...
  • 103
0 votes
1 answer
25 views

Why do we always use static pressure when thermodynamic formulas?

For example: Why do we use static properties when deriving the speed of sound equation? Why isn't dynamic pressure considered in the process nor in the resulting formula? $$ \sqrt{k\frac{P}{\rho}} = c$...
  • 21
0 votes
1 answer
44 views

How air dam reduce drag and lift?

Few questions about air dam(flexibile vertical plate on front bumper) What is main purpose of air dam in car industry, reduce drag or reduce lift(increase downforce)? How dam reduce drag if : a)...
  • 175
2 votes
0 answers
21 views

Why is enthalpy the same in an isentropic and in an actual stagnation process?

I'm learning about stagnation, and currently I'm comparing an isentropic and an adiabatic process where the enthalpy stays the same. The diagram below helps to illustrate my point. I can't see why the ...
  • 21
0 votes
4 answers
44 views

best way to seal 5mm pipe?

I'm working on a personal hobby extending the reach of my pressure sprayer, I'm using 5mm pipe to connect it all together, the issue I'm running into is once I start pumping pressure up, the little ...
-1 votes
2 answers
34 views

Incompressible Fluid Flow in horizontal pipe segment which encounters tilted pipe segment - Continuity Equation

Say that we have water flowing horizontally in a pipe of constant diameter. The continuity equation for incompressible fluids, which is a statement of mass conservation, guarantees that the flow rate ...
  • 99
0 votes
1 answer
18 views

Some variables relation for the Turbulent flow

I have the internal area of the pipe(ft^2), flow rate(gpm at 7ft/min), Reynolds number, pressure drop(psi/100ft), and pressure drop(ft/100ft) shown on the flow table as attached. May I know what ...
  • 1
1 vote
2 answers
34 views

Anemometer in liquid

Does anyone know if there's an anemometer for fluid flow, or any speed measuring apparatus, that can work in liquid? I am planning to use it to demonstrate natural convection circulation.
  • 111
0 votes
0 answers
13 views

Pressing a fluid onto a structure in ANSYS Fluent

I have a spefific problem which I tried to solve with Ansys Fluent and Transient Structural but I did not manage to get a solution so far. I am happy for any kind of help. I want to press a block of ...
  • 1
0 votes
0 answers
40 views

Water Pump Selection Guide for Robotic application

Actually, I'm attempting to construct an Arduino firefighting vehicle. I am aware that a pump would be necessary for it to function. My a few questions are listed below. Despite my research on pumps, ...
  • 1
1 vote
1 answer
46 views

How to find the downstream flow depth when the discharge is not given (2 unknowns)?

Example problem: case 1 is simple as the discharge is given and all I have to do is use some formulas. But case number 2 is different as discharge is not given. How do I go about to solve this? So ...
1 vote
1 answer
52 views

Is supersonic flow not possible in a venturi tube?

I'm trying to design a venturi tube that will have a pressure drop of 91525 Pascals where the inlet pressure is at 1 atm and the throat pressure is at 9800 Pascals. I calculated the minimum throat ...
0 votes
0 answers
23 views

why the gage pressure of a fluid is zero at locations where the HGL intersects the fluid?

I have searched for answers to this, but so far I have not found any consistent answers. Please, may anyone help me understand this.
0 votes
1 answer
29 views

Calculating the leakage of water in a pressurized vessel based on initial and final pressures?

Let's say you have a piping system containing liquid water under high pressure. One section of the pipe of ~70L gets isolated, and it is initially at the same pressure as when it was isolated, which ...
1 vote
1 answer
31 views

Which are the Betz's limits for marine devices such as wave energy converters?

Nowadays, climate change is a relevant topic to reflect on the uses of renewable energies, such as the Sun, wind, oceans, tides, etc. Engineers are trying to design devices to extract the most power ...
0 votes
0 answers
12 views

How can I derive the equation for the spectral density of the subgrid-scale (SGS) dissipation

I need to derive the equation of the spectral (power) density of the subgrid-scale (SGS) dissipation $\tau_{ij}\bar{S}_{ij}(\kappa)$. I know how to derive the filtered energy equation (LES) $\frac{D ...
  • 1
3 votes
2 answers
74 views

Why do we need continuum approximation in fluid mechanics?

We know that a fluid in reality is not continuous. It has spaces and voids between atoms and molecules. Continuum approximation is a famous approximation that is taken in any fluid mechanics textbook. ...
0 votes
0 answers
17 views

How can I check boiler blowdown sample line compliance with international code such as velocity= 1.5 to 1.8 m/s and flow 1000 ml/min

looking to cross verify this blowdown sample line with below given data against International code such as Velocity: 1.5 to 1.8 m/sec and flow 1000 ml/min. Data available: Location of sample line: ...
  • 1
0 votes
4 answers
30 views

Choosing the right pipes for a combination of peristaltic and circulation pump

I would like to circulate the water within an aquarium that contains around 30l water with a circulation pump and an active chiller that contains R134a cooling fluid. New water shall be sucked with a ...
0 votes
1 answer
22 views

Minimum thickness for a pipe fitting?

I need to thread a 1/4 bsp (M12) into a 4mm thick aluminium end plate. The working fluid is water at 90 degrees celsius. Is the end plate thick enough to adequately seal the flow or should I consider ...
  • 1
1 vote
4 answers
668 views

Ship Stability And Overturning Moment

Here a ship that is tilted due an external force . the buoyancy and weight force will create an overturning couple that will rotate the ship in the clockwise direction. Now, the moment equation was ...
-1 votes
1 answer
50 views

Volume flow rate associated with pressure loss in a pipe

We all know the formula for volume flow rate is, Q=Vavg·A, and that it is constant through a pipe. Now, when a fluid flows in a pipe, a pressure drop will happen thus velocity will decrease and, again ...
2 votes
2 answers
55 views

Direction of tube when measuring air flow

When doing pitot tube measurements, the pressure is measured in 2 places. At the wall (A), for the static pressure and against the flow (B), for dynamic pressure. Where the difference between these ...
  • 21
0 votes
1 answer
35 views

How ground water is brought to surface if maximum suction head is limited to 10 meter?

The [depth of groundwater is around 15 to 90 meters][1], while the maximum suction head that can be [created is limited to 10 meters][2] than how this 15 to 90 meters suction head is generated? [1]: ...
0 votes
1 answer
69 views

Calculate steam flow rate with pressure difference

So I have a 4-inch pipe with a pressure of 1.5 bar drop to 1.01325 bar, with a temperature of 120 degrees Celsius. How can I calculate or estimate the steam flow rate for this system?
5 votes
1 answer
93 views

Liquid splashes - who researches it, and why don't all urinal mats look the same?

I normally wear shorts in the summer, at which point I become very aware of the problem every man knows about - splashback of pee from urinals. No matter how you stand or aim, the inherent splashing ...
  • 571
2 votes
1 answer
28 views

Analyzing the term $\frac{1}{c_s^2}\frac{dP}{dz}$ for atmospheric phenomena?

Some background I am reading through a textbook on atmospheric fluid dynamics. The author is discussing something called the Boussinesq relations, and eventually the following expression arises: $$ \...
  • 65
0 votes
0 answers
16 views

What is the physical and mathematical meaning of nonsymmetric mass, damping and stiffness matrix of a linear fluid-solid interaction modeling problem?

Suppose the problem of the subsonic flow over a simply-supported rectangular plate as bellow. According to the assumptions of incompressible, inviscid and irrotational flow, and using perturbation ...
  • 1
0 votes
0 answers
24 views

How (mathematically) does pressure in the intake manifold vary based on size of throttle opening?

I have the intuitive picture somewhat down: the intake manifold is partially opened; during the intake stroke of a four-stroke process, the piston moves rapidly moves downwards creating a short-term ...
  • 1

1
2 3 4 5
21