Compressible Definition and 80 Threads

In thermodynamics and fluid mechanics, the compressibility (also known as the coefficient of compressibility or, if the temperature is held constant, the isothermal compressibility) is a measure of the relative volume change of a fluid or solid as a response to a pressure (or mean stress) change. In its simple form, the compressibility



κ


{\displaystyle \kappa }
(denoted β in some fields) may be expressed as




κ
=



1
V






V



p





{\displaystyle \kappa =-{\frac {1}{V}}{\frac {\partial V}{\partial p}}}
,where V is volume and p is pressure. The choice to define compressibility as the negative of the fraction makes compressibility positive in the (usual) case that an increase in pressure induces a reduction in volume. The reciprocal of compressibility at fixed temperature is called the isothermal bulk modulus.

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  1. M

    VBA Excel Functions for Compressible Flow. Houghton and Brock Tables

    G'day! This is my first post on this forum and I hope you find it usefull! Attached are complete set of Excel functions for *Isentropic Flow *Prandlt Meyer Expansion *Raleigh Flow *Fanno Flow *Plane Normal Shock *Plane Oblique Shock They are contained in the attached workbook (zipped as it...
  2. R

    Is Temperature or Pressure Different at Inlet and Exit in Compressible Flow?

    Hi I was wondering, if a flow is compressible, then does that mean that if the inlet and exit of the control volume (same C.S. area) have different densities, would that mean that the temperature and/or pressure of the exit be different than at the inlet (assuming ideal gas)? If this were...
  3. F

    Compressible vs. Incompressible Flow Equations

    As a private study I'm trying to figure out fluid dynamics applied to compressed air systems. Most of the material I am studying considers only incompressible fluid flow. From what I understand about the differences between compressible and incompressible flow in terms of the equations it only...
  4. M

    Heat Equation for Compressible Fluids: Valid or Not?

    Hi everyone, I am wondering if the heat equation is valid for compressible fluids like air. This is assuming constant 100% humidity. If it is not then how close is the appoximation. The model assumes that heat moves through an array of air only by conduction. At the moment I use a...
  5. U

    Understanding what a stagnation point is in compressible flow

    Suppose we have a flow of a fluid and let it flow (in x direction) into a stationary wall..the x velocity becomes zero...is this an example of stagnation point? If not, please cite an example of when that is true.
  6. D

    Isothermal compressible flow in horizontal pipe

    Homework Statement A compressor is required to drive acetylene gas at 1.85 kg/s through a horizontal pipe, 68.7 m long. The maximum pressure that may be developed by the compressor is to be found, and gas pressure at the delivery end of the pipeline must be 470 kPa. The system is to...
  7. K

    Exploring Subsonic, Compressible Flow in Curved Ducts

    Hi, I'm new here so I'd like to apologise in advance if this has been posted before. I tried searching first but nothing came up. I'm doing a project on subsonic, compressible flow in curved ducts and have a question about the physics involved as the flow navigates a bend. Allow me to...
  8. E

    Expansion of a Compressible Gas

    Hi, I'm trying to figure out the pressure exerted by a compressible gas (air) after it has expanded out of a cylinder for a simple conceptual design. I'm pretty sure that it's a simple problem, but I'm a little thickheaded atm. Here is my thinking so far: Due to the compressibility of air...
  9. G

    Compressible Flow Homework: Show Particles in Cube Occupying Volume e at t=1

    Homework Statement Consider the flow with velocity vector v = xi. Show that the individual particles have the position vectors r(t) = c1eti + c2j + c3k with constant c1, c2, c3. Show that the particles that at t = 0 are in the cube whose faces are portions of the planes x = 0, x = 1, y = 0, y...
  10. T

    Hydraulic press and compressible fluids

    Hi everyone, I did not get a reply in 3 weeks under mechanical engineeting... trying here. Here is practical question mixing compressible and none compressible fluids with a hydraulic press. Can the following actually work ? I believe it can but some experience people in this field looking...
  11. B

    Can Air Be Compressed Without a Container?

    I have read in different theorem's (Bernoulli's for example), that free air is considered incompressible below a speed of 0.4 Mach. If I were to place air in a jug and reuce the amount of space it occupies, then I am compressing it, but is this possible under certain conditions in free air?
  12. T

    Hydraulic press and compressible fluids

    Hi everyone, Here is practical question mixing compressible and none compressible fluids with a hydraulic press. Can the following actually work ? I believe it can but some experience people in this field looking at it may prove me wrong. Say we have a sphere, 1 cubic meter in volume. The...
  13. K

    Comparing pressure losses in compressible flow between air and natural gas

    Hi! I have experimental data measuring losses across an obstruction in compressible flow which basically consists of static pressure, total pressure and total temperature upstream of the obstruction and the same variables downstream for a number of different mass flow rates. This data was...
  14. J

    Combustion and Compressible Flow

    Hi, I'm currently a student and learning these two topics for a module. I've searched the net for many references but can't find anything that is really that helpful. Can anyone reference me any good links to questions and solutions regarding these topics? Also any books you guys would...
  15. K

    Energy loss in compressible flow

    I have air flowing through a gate valve with lengths of pipe of matching diameter upstream and downstream. At a certain distance from the valve upstream and downstream, I am measuring static temperatures and static and stagnation pressures. I can estimate the Mach numbers at the tapping points...
  16. J

    Compressible Fluids: Getting Desired Volume/Mass Flow Rate

    I'm having trouble calculating the required pressure to get the desired volume flow rate (at outlet conditions). I'm no expert at compressible fluid systems, but I ended up being the one to design it... The system must feed helium vertically through 3/8" ID, 112 ft long tubing (ID can vary, I...
  17. B

    What soft compressible materials safely work with wiring

    Hello I am a student working on at home project and I need help on choosing a compressible, soft material that works safely with wiring and electricity. The kind of material I need is something that is compressible and soft, sort of like a foam or gel heal pad that people put in their shoe. The...
  18. A

    Compressible Flow: Flow in nozzles

    Homework Statement I am currently studying for finals, and I am really confused about compressible flow in nozzles. Some questions I have: 1) What is exactly is the condition for choked flow for converging, diverging, and converging-diverging nozzles? 2) When can we assume that the back...
  19. C

    Diving Board Stress Points: Shear, Compressible, & Normal

    Hi, This is not homework but out of curiosity. On a diving board where are the points where stress is applied? Including shearing, compressible, and normal stress? Thanks
  20. J

    Finding Outlet Diameter for Compressible Fluid Flow

    hii , i know the inlet conditions i.e. dia 2mm , pressure = 100 bar, density= 0.001176 m3/kg, mass flow rate remains constant= 0.09017 m/s , for same mass flow rate for pressure drop 80 bar(i.e. pressure at outlet is 20 bar) for COMPRESSIBLE FLUID what will be the outlet dia? take fluid carbon...
  21. J

    Calculating Head Loss from Enlargement in Compressible Fluid

    how to calculate head loss due to sudden enlargement in case of compressible fluid? hiiiiii guys, am graduate student, i want to know @ head loss in case of compressible fluid due to sudden enlargement...pls help me ...as soon as possible...
  22. M

    Difference between compressible and incompressible flow

    Hi all I am really confused with what is the actual meaning of compressible and incompressible flow?
  23. D

    What are some real-world examples of compressible fluid mechanics in action?

    Hi Guys, I know that the compressible Euler Equations are: \partial_t (\rho \mathbf u) + (\mathbf u \cdot \nabla)(\rho \mathbf u) + \nabla p = 0 \partial_t \rho + \nabla \cdot (\rho \mathbf u) = 0 Subject to suitable initial conditions and solving for \mathbf u, \; \rho unknown...
  24. V

    Compressible or imcompressible?

    Hello, I'm doing the simulation by using the CFD Fluent. The reactor is 10 cm diameter and 1 m height. There is the water inlet (15mm) tangentially to the wall at the bottom end to produce the upward vortex flow. and the air-bubble injection axially at the middle of bottom end. The...
  25. A

    Deriving Conservation of Mass & Momentum for an Inviscid Compressible Gas

    Homework Statement Starting from the equations of conservation of mass and momentum for an inviscid compressible gas, \frac{\partial \rho}{\partial t} + \bigtriangledown . (\rho {\bf u}) = 0 \rho ( \frac{\partial {\bf u}}{\partial t} + ({\bf u}. \bigtriangledown){\bf u}) = \bigtriangledown...
  26. L

    Bernoulli's Principle on Unsteady State and Compressible Fluid

    Do anyone know about any website were the Bernoulli equation is developed from the Newton Second law and without the assumption of steady state and incompressible fluid? With differential calculus, please. My textbook just give out the equations for unsteady state and incompressible, but I...
  27. C

    Can 25 PSI Methane Flow Through a 3/8 Pipe Meet a 392,000 BTU/hr Demand?

    What are the governing equations for compressible fluid flow? Specifically; methane gas inlet pressure of 25 psi through a 3/8" dia. pipe and I need to relate this to a methane flow of 392,000 BTU/ hr @ 55-60psi 59 F and RH 60% (i.e. ISO 2314) through an as yet undetermined diameter pipe...
  28. M

    Compressible air flow thorugh pipe

    Hi guys: I am wondering with issue regarding high speed (subsonic) compressible air flow thorugh a pipe exit to atmosphere. So here is detail: Air coming from a reservoir and flowing thorugh an adiabatic constant area pipe and exit to atmosphere at the end of the pipe. Due to high...
  29. I

    Compressible Fluid Thermodynamics

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  30. S

    Compressible Navier Stokes in cylinder coordinates

    Hello, I need the Navier Stokes equations for compressible flow (Newtonian fluid would be ok) in cylinder coordinates. Can anybody help? Thanks
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