# Mechanical Engineering - Hydraulics and Fluid Mechanics - Discussion

2.

The velocity corresponding to Reynold number of 2800, is called

 [A]. sub-sonic velocity [B]. super-sonic velocity [C]. lower critical velocity [D]. higher critical velocity

Explanation:

No answer description available for this question.

 Gowtham said: (Oct 6, 2013) If re>2000, the velocity is called critical or turbulent flow.

 Ankit Dadhe said: (Feb 19, 2014) When is it call sonic & super sonic?

 Girish Changavi said: (Apr 7, 2014) If Re >2000, tts laminar flow. If Re < 4000 its turbulent flow. If between 2000 to 4000 its transition flow. Here Re is 2800 so its higher critical velocity.

 Manoj said: (Aug 12, 2014) @Girish for turbulent flow Re>4000.

 Prateek said: (Sep 3, 2014) Ankith sub sonic & super sonic is measured with the help of Mach number.

 Shobhit Kumar said: (Jan 25, 2015) When mech number <1 the flow is sub sonic. When mech number =1 the flow is sonic. When mech number lies between 1 to 6 the flow is supersonic. When mech number >6 the flow is hyper-sonic.

 Swapnil said: (Feb 3, 2015) What is relation between Reynold number & mach number?

 Prasad said: (Sep 23, 2015) There is no relation between mach number and Reynolds number, Mach number is used to measure the speed of sound waves and Reynolds number is used to measure the type of the flow. Mach number is the ratio of flow velocity to the speed of light.

 Muhammad said: (Oct 22, 2015) @Prasad. Ratio of flow velocity and peed of sound.

 Rahul said: (Nov 9, 2015) Lower Critical Rn value for Circular Pipes = 2000. Higher Critical Rn Value for circular Pipes = 4000. The answer for given question should be in transition i.e. neither lower nor higher velocity.

 Denish said: (Mar 6, 2016) It is right if Re>2000 then it is called critical but this is true only when flow through pipe. But for different flow conditions Re. Value are different. In this question they have not mention any type of conditions then how we can decide the right answer.

 Harry said: (May 24, 2016) Low critical velocity is laminar flow. High critical velocity is turbulent flow. Here they give 2800 is laminar flow so, it should be a low critical velocity.

 Srikantha A said: (Sep 20, 2017) The flow at which laminar flow stops is called lower critical velocity (RN 2000). The flow at which turbulent flow starts is called higher critical velocity (RN 2800).

 Tagese said: (Oct 15, 2017) @Girish Changavi, It should be If Re <2000, tts laminar flow. If Re > 4000 its turbulent flow. If between 2000 to 4000 its transition flow. Here Re is 2800, so it's not higher critical velocity.

 Naveenkumar T said: (Nov 25, 2017) If Re <2000, tts laminar flow. If Re > 4000 its turbulent flow. If between 2000 to 4000 its transition flow. The velocity at which flow changes from laminar to transition is called LOWER CRITICAL. VELOCITY and that at which transition changes to turbulent is called UPPER CRITICAL VELOCITY.

 Nirav said: (Dec 13, 2017) Yes, you are totally right @Naveenkumar T.

 Aakash said: (Jan 5, 2018) Raynold number = 2800 shows that flow is changing from the transition to turbulent and for this kind of flow, velocity is termed as upper critical velocity. When flow changes from laminar to transition velocity is termed as lower critical velocity.

 Aakash said: (Jan 5, 2018) Raynold number = 2800 shows that flow is changing from the transition to turbulent and for this kind of flow, velocity is termed as upper critical velocity. When flow changes from laminar to transition velocity is termed as lower critical velocity.

 Kavya said: (Jan 6, 2018) What if Reynolds number =2000?

 Aniruddh said: (Sep 7, 2018) It's not given whether the flow is in a pipe or flat plate?

 Himanshu Mittal said: (Feb 27, 2019) If flow changes from laminar to transition implies lower critical and from the transition to turbulent implies higher critical. Re 2800 means transition flow to laminar ie upper critical.

 Sarath said: (Apr 12, 2019) When Reynold's number is between 2000 and 2800, the flow is neither laminar nor turbulent. The velocity corresponding to Reynold's number of 2000, is called lower critical velocity and the velocity corresponding to Reynold's number of 2800, is called higher critical velocity.

 Raushan Kumar said: (Oct 6, 2019) Flow in pipes Re <2000 - laminar. Flow in pipes Re 2000-4000 - transition. Flow in pipes Re >4000 - turbulent.

 Raushan Kumar said: (Oct 6, 2019) Higher critical velocity-at which flow changes from transition state to turbulent.

 Kamal said: (Jul 14, 2020) Re<2000 laminar flow, Re>4000 turbulent flow. So it is 2800 turbulent flow high critical energy. Mach no<1 subsonic flow, Mach no=1 sonic flow, Mach no>1 supersonic flow special case Mach no. 1to6 hypersonic flow.

 Mahe I said: (Apr 28, 2021) So Mach number depends on the speed of sound waves and Reynolds number used to measure type of flow and Q asked type of velocity not a flow.