Mechanical Engineering - Hydraulics and Fluid Mechanics - Discussion


Bulk modulus of a fluid __________ as the pressure increases.

[A]. remains same
[B]. decreases
[C]. increases

Answer: Option C


No answer description available for this question.

Bhaskar said: (May 13, 2013)  
Bulk modulus = Change in pressure/(- volumetric strain).

Anil Kumar said: (Jan 3, 2015)  
Change in pressure/(- Change in volumetric strain).

Sonal Shrivastav said: (Jan 18, 2015)  
Bulk modulus is a constant quantity. As we change the pressure, there will be corresponding change in volume as well.

Darshan Kathiriya said: (Mar 4, 2015)  
It should remain same since Bulk modulus is a property.

Zxc said: (Apr 18, 2015)  
Strictly speaking, the bulk modulus is a thermodynamic quantity, and in order to specify a bulk modulus it is necessary to specify how the temperature varies during compression: constant-temperature (isothermal KT), constant-entropy (isentropic KS) , and other variations are possible. Such distinctions are especially relevant for gases.

For an ideal gas, the isentropic bulk modulus KS is given by KS = γ, p.

And the isothermal bulk modulus KT is given by KT = p.

γ is the heat capacity ratio.
P is the pressure.

When the gas is not ideal, these equations give only an approximation of the bulk modulus. In a fluid, the bulk modulus K and the density ρ determine the speed of sound c (pressure waves), according to the Newton-Laplace formula.

C = sqrt{K/ρ}.

In solids, KS and KT have very similar values. Solids can also sustain transverse waves: For these materials one additional elastic modulus, for example the shear modulus, is needed to determine wave speeds.

Vikrant said: (Apr 18, 2015)  
The concept of the bulk modulus is mainly applied to liquids, since for gases the compressibility is so great that the value of K is not a constant.

Sintu Paul said: (Apr 15, 2017)  
Bulk modulus of liquid is the ratio of Inertia force to elastic force, which is also called Mach no or Cauchy's no.

So, if pressure increases then elasticity will be less, Then obviously Bulk modulus will be more or increase.

Vinoth said: (Jun 25, 2017)  
For material it is constant.

But for fluids, especially gas.
Bulk modulus = p(isothermal).
= Y p (adiabatic).
Y~ heat capacity ratio.
Here it mentioned fluids so ans is increase with pressure.

Kishan Ahir said: (Apr 13, 2018)  
It's become harder and harder to compress fluid that's why when we increase pressure bulk modulus also increase.

Biprojit said: (Apr 23, 2020)  
Well said @Kishan.

Sachin said: (Apr 10, 2021)  
No, The very fact that E, (C, N or G), K and 1/m are called elastic constants and their values are determined experimentally. When E and 1/m are constants, how can K vary?

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