Flow Definition and 1000 Threads

I would like to ask about the difference between the simple compressible system and the flow systems. "In the absence of such effects as magnetic, electric, and surface tension, a system is called a simple compressible system. The total energy of a simple compressible system consists of three...

Anyone knows if i can calculated Nusselt number for a developing turbulent flow in the entrance region for a duct/ tube?

Hi PF! Can someone help me understand the development of a laminar jet flow? Perhaps @Chestermiller and @boneh3ad have some advice? Thanks!

I am trying to calculate the flow in a system from an underground tank up through a pump into a vessel. But cannot find or derive a formula that yields a good result, I don't think I can use the same head calculations as Velocity will have changed. 1. Homework Statement ρ = 1000 kg m–3 μ =...

Homework Statement An Aluminium rod has a diameter of 40mm. and is 750mm long. If the temperature difference between the ends of the rod is 100C . Take the thermal conductivity of Aluminium to be 235 Wm-1K-1 Homework Equations k * A * ΔT / L The Attempt at a Solution 235 * 0.097 m * 100 /...

Homework Statement A tank with a 25.5 litre capacity contains air compressed into 355 atmospheres used to drive a torpedo by expansion into an engine via a pipe of diameter 0.08cm. A mechanism ensures that the gas flows to the engine at a constant rate and any cooling of the air during...

I encountered this statement on my lecture notes today, I don't understand why compressible flow needs to have another constraint of energy equation while incompressible flow only satisfies continuity and momentum equation. And how is this energy equation related to the speed of sound?

Can someone explain what it means for a fluid flow to be reversible and how this relates to Reynolds number, both intuitively and mathematically? Thanks!

Homework Statement A fireman's hose acting as a water cannon, directs 100 litres/s (100 kg/s) of water horizontally at your chest at speed 5 ms-1. Assuming water essentially falls to the ground after hitting your chest (rather than say reflecting horizontally backwards), what horizontal force...

Hi. I fear I might not have understood some fundamental concepts about electric power transmission. So we have "neutral" which is brought to Earth potential. Does this mean the electrical circuit from the power plant over highly conductive aluminium cables to my home closes back to the power...

So I was playing around with Fluid Pressure and Flow over on PHET animations and noticed something odd. When a fluid with high flow rate is going from a large pipe to a small pipe a lower density increases the pressure. And a higher density lowers the pressure in the narrow part of the pipe. My...

Consider a small rigid spherical particle of radius a, fully immersed in a viscous incompressible Newtonian fluid of shear viscosity η above a hard-wall with stick (no-slip) boundary conditions, located at the plane z = 0. A constant positive (external) torque Tx is applied on the particle. My...

Hello, I am building a small car that upon hitting a wall will go backwards, in other words reverse the current flow. I have all the components requiered (resistors 3k and 1k, wires, 6V battery, and an H-bridge, locking button) only thing I do not know is how to connect them all together. If...

Homework Statement This problem belongs to the Intermediate Physics for Medicine and Biology, Hobbie Chapter 4. The heat flow equation in one dimension $$ j_H=-\kappa \partial_x T $$ where ## \kappa ## is the termal conductivity in ## Wm^{-1}K^{-1}##. One often finds an equation for the...

looking at where to start understanding how the thrust/lift generated by a specific propeller (hypothetical one) changes as a function of surrounding air pressure. obviously the lift will go to zero as air pressure decreases. as pressure increases, modeled by say mounting the propeller inside...

Would lightning work in space? I think it would but you wouldn't be able to see it? Let's say I have some sort of device that creates a lightning bolt, if I shot it at a watermelon in a vacuum or another target would it hit the target, or nothing happen because of the vacuum?

Hi PF! Can someone help me understand how to draw lines of constant pressure in an inviscid flow field, say flow around a cylinder. I am having trouble understanding how to draw these. Any help is greatly appreciated! I ask this question because I am preparing for the Q exam for PhD and one of...

If I have a 1/2" source hose with 60PSI and a Flow sensor then split to four 3/8" hoses with a flow rate limited to 30SCFH. Should I expect to have a 120SCFH flow rate across my flow sensor? The gas will be 90% Argon/10%CO2, but we could assume an Ideal Gas for this... Right? I understand...

Hello, How do you calculate the terminal velocity of a fluid through a pipe. My problem includes turbulent flow, very high reynold number, and water (incompresible).

I'm trying to figure out how to best filter some liquids. A 5 gal bucket is filled with some filter medium (say sand on top 1/2 and fine charcoal on bottom 1/2). The liquid is slowly added at the top and gravity is used and vacuum may be used at some point with a complete seal along the bottom...

Hello, I have a general question regarding energy coupling in multi phase flow. My question comes is based on the text from this book...

I got two flow lines at 90 degree angle, Line A carrying acid and line B carrying water, each with 1 inch diameter, merging at point P. The third line C beginning at point P, also 1" diameter, should carry 90% water and 10% acid. I came up with option 1 but not sure how to achieve the same using...

A water tub has 3 water channels. Channel I and II for filling the tub and channel III to empty it. Those 3 channels together fulfill the tub for 1 hour and 20 minutes. Channel I and II together fulfill the tub for 1 hour and 12 minutes from the empty condition. Channel II and III together...

Hi all, It has come to my attention this article on PF (https://www.physicsforums.com/insights/can-gene-editing-eliminate-alzheimers-disease/) about a genetic approach to prevent Alzheimer's disease, based on applying gene-editing techniques on human embryos. In short (so not to be...

Hello, I'm a physician with special interest in cardiovascular physiology. I'm trying to comprehend the basic physics of the cardiovascular system. Here's my thought process - Simply stated - the heart muscle contracts, thereby causing a reduction in the cardiac chamber volume and release of...

Why is the pressure used in flow work the pressure of the fluid? If the fluid was say at 10kPa and the external pressure was at 0Pa, why don't we use the 0Pa in our calculations for flow work, since it's the external pressure that's the resistance? Or is it not possible to have this difference...

I'd like to experimentally simulate air flow turbulences around obstacles. Building the obstacles in one thing, but providing a well characterised flow (and mix it with something visible like smoke...) is something else. In general, I think the whole idea is easier to acomplish compared to fluid...

Hi PF! Some classmates and I were talking about the streamlines around a submerged cone being pulled at a velocity ##V##. The picture is attached. Can someone shed some light on the streamlines of this flow, assuming it is inviscid? I take a frame of reference that moves with the cone...

What is the intuition behind the fact that stokes flow is time reversible?

Hi PF! I was recently looking at two immiscible fluids in a 2-D Poiseuille Flow with two immiscible fluids of different densities. Let the total distance of the channel be ##L+\epsilon L##, where the dividing line between the two flows is ##L##. I was thinking of the possible flow profiles and...

Hi When I was writting my thesis I found in an article, published in International Journal of Heat and Mass Transfer, an unit of mass flow rate G - kg/(m^2*s). Isn´t it wrong? I think that the unit of mass flow rate is kg/s. Would you mind helping me to figure it out? Thanks.

So, a coworker approached me today with a 'simple problem' to solve, looking to sanity-check a design choice. Much to my dismay, I had no idea how to approach it. Worse, google had no straight-forward answers either, and any formulae I did find seemed circular. This seems too simple to...

Hi, I recently came across a blog on schlieren visualization (http://ottobelden.blogspot.in/2010/07/homemade-schlieren-photography-setup.html). I replicated it with the following: Convex lens (130 mm dia and 350 mm focal length), LED light source (5 mm white LED) and smartphone camera (Moto G4...

As I understand it, there is no solid definition of time other than the entropy is an arrow of time flow. I believe that physics equation would work regardless of the direction of time flow. What would be the implications if we assume that past, present, and future events are part of the...

The momentum-space fermion propagator in the free Dirac theory is given by The arrow on the fermion propagator is said to represent the flow of charge. How can we derive this statement quantitatively from the Dirac Lagrangian? What is the quantitative form of the charge being referred to here?

Hello! Let's say your house is connected to the local distribution grid, and you also have a PV-system on your house that is connected to the grid (no storage): How does the equipment in your house "use" the power from the PV module, and not "from" the grid? Everything is connected, right? If...

Hello all, I'm a Mechanical engineer with no prior experience in designing flow systems. I'm struggling with a hydraulic system that I have to design. the number of unknowns is large. but maybe by dividing the system to small sections, a solution can be found. I attached a schematic drawing...

Liquid is being pumped into a vessel then it leaves and recirculates through the pump. I have calibrated the pump by measuring the amount of fluid being pumped through the tube (not into the vessel). However I have noticed at low flow rates the liquid level at the inlet is only half full! That...

Homework Statement I am given the following interaction, $$\pi^-+p\rightarrow \pi^++\pi^-+n,$$ and asked to draw the Feynman (quark flow diagram). Homework Equations None; just baryon number conservation, quark flavor conservation, etc. The Attempt at a Solution First, as baryon number and...

Hey guys! Any answers will be much appreciated! The following is a deep conceptual issue I have. The diagram is a bit crude but will suffice I think. Note: Had drawn the circular 'electric field' at the time, to just help myself over my confusion. Feel free to ignore it. As per Ohm's law V...

Hi Friends, I am Milind Nachane, New member of PF. We have to buy a Water Treatment Device which eliminates the scaling and rusting Hazard. To decide model of device we need to know Flow rate of Pump. I know that Pump is Mono-block (Non-submersible) of 7.5 Hp and has 2 Inches Diameter...

Homework Statement I have no idea how the third formula of dy/dx is derived ... Homework EquationsThe Attempt at a Solution I know that the Q = (1/n)(A)(R^2/3) [(s)(^0.5)] , Q = K [(s)(^0.5)] , so , K= (1/n)(A)(R^2/3) i know that for very wide channel , y = R A = by K= (1/n)(A)(R^2/3)...

Hi I just finished a good intro to aerodynamics but I want to understand taylor couette flow. My book stopped at 2d couette flow between 2 plates. I need a good book that someone with only an intro to Aero can understand! Any recommendations?

Homework Statement I am not sure how to get the Mmin . Why δA will become B (refer to the pink circled part) Homework EquationsThe Attempt at a Solution Is there anything wrong with the author's steps ? I know the author's intention is to show that the Mmin occur when the Fr = (Q^2)B/ g(A^3)...

The equation for mean arterial pressure = flow * resistance, however, if we increase flow we would increase velocity by the equation Velocity = flow/ cross sectional area, and velocity would decrease pressure according to bernoullies law? Which would take precedence in generating more pressure...

I've made a fluid flow simulator, for anyone interested in fluid dynamics. The simulator models some basic flows which I learned on a 2nd year fluid dynamics course. It doesn't include viscosity, density or whatever else (hence for example the flow past a sphere in the simulator is a perfect...

Homework Statement How to show that the dE/dy = 0 , yc will become (Q^2 / g)^1/3 ? http://www.brighthubengineering.com/hydraulics-civil-engineering/53261-open-channel-flow-basics-2-supercritical-flow/#imgn_0 Homework EquationsThe Attempt at a Solution E = y + (V^2) /2g , dE / dy = 1 ... why yc...

Homework Statement In the notes , it's stated in the first part for non-uniform flow that the gradient of $$S_0$$ , $$S_w$$ and $$i$$ are not the same , But , in the lower part , it's stated in the first part for non-uniform flow that the gradient of $$S_0$$ , $$S_w$$ and $$i$$ are the...

Can someone smarter than I, please express p1 and p2 in terms of f, or v and r? The pump pushes out water at f rate which creates velocity v in the bigger pipe. When the water comes to the restriction velocity increases while flow rate is conserved. Bernouli tells us that the change in...

I found it very interesting to see that surface charge and the Poynting vector are being used to describe how a simple DC circuit actually works. Chabay and Sherwood have made an outstanding contribution to physics and engineering in their texts and papers. Of course others jump on the...