The 'specific speed' Ns of a turbine is defined as the speed of a geometrically similar turbine that:
Choose the correct answer
Produces 1 kW under 1 m head
Geometric similar turbine that produces unit power under unit head at unit speed — used for type classification (Pelton/Francis/Kaplan)
Rotates at 1 rpm
Has the highest efficiency
Correct Answer
B. Geometric similar turbine that produces unit power under unit head at unit speed — used for type classification (Pelton/Francis/Kaplan)
Why is this the answer?
Specific speed Ns = N√P / H^(5/4) (power form) or Ns = N√Q / H^(3/4) (flow form). Represents the speed at which a geometrically similar (but unit-sized) turbine would produce unit power under unit head. Type selection: Pelton Ns < 60; Francis 60–300; Kaplan 300–900. Ns is NOT specific to a size — it is a dimensionless similarity parameter for turbine type classification.
Related Fluid Mechanics MCQs
More solved Fluid Mechanics questions for AE/JE Civil Engineering exams.
- The 'tsunami' is distinguished from wind waves by:
- The 'specific energy' in open channel flow is:
- The 'draft tube' in a reaction turbine (Francis/Kaplan) serves to:
- Two identical pumps in 'series' vs. 'parallel' connection:
- The 'flow net' for seepage analysis consists of:
- The 'cavitation' damage to hydraulic turbines and pump impellers appears as:
Practice more Civil Engineering questions
This MCQ belongs to JE Level Premium Test Series. Full tests include timed attempts, rank comparison and subject-wise analysis.