Mechanical Engineering - Hydraulics and Fluid Mechanics - Discussion


The value of bulk modulus of a fluid is required to determine

[A]. Reynold's number
[B]. Froude's number
[C]. Mach number
[D]. Euler's number

Answer: Option C


No answer description available for this question.

Dinesh said: (Jan 2, 2013)  
How will you determine a bulk modules by using mach numbers?

A.Sandeep said: (Mar 17, 2013)  
Bulk modulus is equal to the reciprocal of compressibility.

And Mach number is depends upon the compressibility.

Therefore to determine Mach number bulk modulus is required.

Rohit said: (Jul 7, 2013)  
What is mach number?

Md.Badruddin Saad said: (Jul 11, 2013)  
E = density*dp/change in density. From bernoulli's equation if the order of pressure is same as the order of dynamic pressure then dp=density*velocity square/2. By substituting this in equation for bulk modulus we get. Change in density/density=1/2* (mach. No) square. Where mach number Ma=v/a.

9 velocity of fluid flow/velocity of sound in medium. If change in density/density is < 0. 05 we say fluid is incompressible. So Ma, 0. 33 for the flow to be compressible.

Easwaran said: (Aug 2, 2013)  
Mach no = inertia force / elastic force . It is a dimensionless quantity also defined as ratio of velocity of the flow / velocity of sound. Velocity of sound = sqrt (y. R.T ) y - gama.

Jason Joshwa said: (Aug 31, 2013)  
M = v (ρ / E)1/2.

E - Bulk Modulus of Elasticity.

Vishwa said: (Sep 10, 2013)  
If the value of mach number is 3, then the flow is called supersonic.

Satya said: (Oct 3, 2013)  
Mach number= square root ratio of inertia force to elastic force.

In determining elastic force we need bulk modulus.

Talaviya Vishal said: (Jan 10, 2014)  
Mach number = square root of ratio of inertia force to elastic force. We obtained K by this equation.

Siddharth said: (Jan 17, 2014)  
In fluid mechanics, Mach number (M or Ma) is a dimensionless quantity representing the ratio of speed of an object moving through a fluid and the local speed of sound.

Ankit Dadahe said: (Feb 19, 2014)  
What is bulk modulus?

Nikhil Shukla said: (Mar 14, 2014)  
In simple way bulk modulus define the strength of any material against compression.

Raviteja said: (Apr 8, 2014)  
When compression done on any material,

Thus it will posses a energy those compressed energy is known as bulk modulus.

Akshay Soni said: (Jul 25, 2014)  
The ratio of the compressive or tensile force applied to a substance per unit surface area to change in volume of the substance per unit volume.

Mech@Nical said: (Aug 19, 2014)  
Mach number is the ratio of the square of inertia force to the pressure force.

Manikanta B said: (Nov 25, 2014)  
What is meant by inertia force?

Sachin said: (Dec 19, 2014)  
A force require to keep the fluid at that velocity (moving velocity) or force require to completely stop the fluid.

Ginish said: (Feb 1, 2015)  
In dimensional analysis we use dimensional numbers to check model similarity. In some physical situation elastic force become predominate like inertia force. Mach great scientist introduce a number, which is square root of ratio of inertia and elastic forces to determine similarity between model and prototype.

Here elastic force is product of bulk modulus and area. Thus we need k to determine mach number. And also inverse of mach no is cauchy's no, hence it also need value of k.

Srikanth said: (Mar 14, 2015)  
Mach Number (M).
M<1 = subsonic flow.
M=1 = sonic flow.
M is 1 to 6 = supersonic flow.
M more than 6 = hypersonic flow.

Mach Number Or Cauchy's Number = Inertia force to elastic force.
Euler number = Inertia force to Pressure force.
Weber's Number = inertia force to surface tension force.
Froude's number = inertia to gravity force.
Reynold's number = inertia to viscous.

Prasenjit De said: (Mar 24, 2015)  
Reciprocal bulk modulus of elasticity is compressibility.

Mach number is inertia force/elastic. For bulk modulus machine no require.

Shek said: (Jul 23, 2015)  
Definition of match number?

Radha Choudhary said: (Sep 18, 2015)  
The Mach Number is a dimensionless value useful for analyzing fluid flow dynamics problems where compressibility is a significant factor. (You can also read as-if we compare sound velocity to other velocity then it's called of mach number).

The Mach Number can be expressed as.

M = v/c (1).


M = Mach number.

v = Fluid flow speed (m/s, ft/s).

c = Speed of sound (m/s, ft/s).

Mihir said: (Dec 31, 2015)  
v = (k/density)^0.5.

Mach no = v/c.

So k is required to find Mach no.

Rahul Kumar said: (Apr 2, 2016)  
Mach number = v/c.

c = sqrt(bulk modulus/density).

Vennela said: (Apr 5, 2016)  
Is it is supersonic if Mach number is exactly equal to 3 or if mach no is greater than 1.

Vennela said: (Apr 5, 2016)  
Why we need bulk modulus to find the elastic forces?

Vennela said: (Apr 5, 2016)  
Why we need to use this numbers, and what is Knudsen number?

Sekhar said: (May 3, 2016)  
Mach number is the ratio of the speed of flow to the speed of sound. Where the speed of flow depends on bulk modulus.

Mach number is a dimensionless quantity.

Dad said: (Jun 4, 2016)  

Knudsen number = Free length/characteristic length.

Somesh Garai said: (Oct 20, 2016)  
Alternatively, the Mach Number can be expressed with the density and the bulk modulus for elasticity as,

M = v (ρ/ E)1/2.


ρ = density of fluid (kg/m^3, lb/ft^3).
E = bulk modulus elasticity (N/m^2 (Pa), lbf/in^2 (psi)).

The bulk modulus elasticity has the dimension pressure and is commonly used to characterize the fluid compressibility.

Harshit Mangla said: (Dec 15, 2016)  
Is there any difference between Bulk Modulus and Bulk Modulus of Elasticity?

Shah said: (Jan 13, 2017)  
Not getting this. Please someone explain in detail.

Mahadeb Dey said: (Apr 19, 2017)  
Bulk modulus is equal to the reciprocal of compressibility.

And Mach number is depends upon the compressibility.

Ramakrishnau said: (Jun 26, 2017)  
Thank you all.

Krunal said: (Jul 20, 2017)  
Bulk modulus " the measure of a fluid's resistance to compression "of a hydraulic fluid in position, response time, and stability are critical.

Ashish Baranwal said: (Jul 31, 2017)  
What is Mach Number? How we define?

Suraj said: (Aug 27, 2017)  
Bulk modulus is proportional to pressure. So I think Euler's number is the correct answer. It is the ratio of inertia force and pressure force.

Sayali said: (Oct 22, 2017)  
Euler number = pressure force to inertia force.
Reynold no= inertia force to viscous force.
Froude no=inertia force to external force.

Upendra said: (Jan 8, 2018)  
Bull modulus is directly proportional to the pressure that why it may be used for determine the eulier number.

Srilakshmi said: (Jan 10, 2018)  
MACH NO OR CAUCHY'S NO IS the ratio of inertia force to elastic force & also ratio of speed of flow(v) to velocity of sound(c) so,

c= √K/row(p).
k is bulk modulus.

Praveenkumar Kanthegol said: (Mar 10, 2018)  
Bulk modulus - (SOM), It is the ratio of volumetric stress to volumetric strain. In Fluid mechanics it is the ratio of compressive stress to volumetric strain. Both sentences are same. And compressibility is the reciprocal of bulk modulus of elasticity.

Kaydee said: (Jul 28, 2018)  
Mach Number can be expressed with the density and the bulk modulus for elasticity as;

M = v (ρ/ E)1/2.

ρ = density of fluid (kg/m3, lb/ft3).
E = bulk modulus elasticity (N/m2 (Pa), lbf/in2 (psi)).

P Shiva said: (Sep 18, 2018)  
Thank you for the explanation.

Naeem Shahzad said: (Jun 30, 2022)  

Don't you think that bulk modulus is the ratio of stress /strain? Please explain.

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