Inward Flow Reaction Turbine — Flow Direction Through Runner In an inward flow reaction turbine, how does the water move through the runner relative to the wheel radius?

Introduction:
Reaction turbines exchange energy with the fluid across the runner as pressure changes occur. Their classification by flow direction clarifies the geometry of inlet and outlet. This question focuses on the classical inward-flow reaction arrangement.

Given Data / Assumptions:

• Steady operation; water is incompressible.
• Runner passages guide flow radially inward.
• Neglect minor 3D effects; consider idealized runner.

Concept / Approach:
In inward-flow reaction turbines, water enters at a larger radius (outer periphery) with higher absolute velocity and static pressure, and discharges at a smaller radius (towards the centre), transferring energy to the runner through a drop in both pressure and absolute velocity components as guided by the blades.

Step-by-Step Solution:
Identify turbine type: inward radial flow.At inlet (outer radius), absolute velocity has tangential and radial components designed to match blade speed and incidence.Through the runner, radius decreases, static pressure and whirl adjust, doing work on blades; discharge approaches inner radius.Hence, motion is from outer periphery towards the centre.

Verification / Alternative check:
Velocity triangle sketches for inward reaction turbines show positive work extraction with decreasing radius and appropriate whirl reduction.

Why Other Options Are Wrong:

• Parallel to axis: describes axial-flow machines (e.g., Kaplan).
• Centre to periphery: outward-flow type, not inward.
• Partly radial and partly axial: mixed/diagonal flow machines, not purely inward radial.

Common Pitfalls:
Confusing inward radial turbines with axial-flow turbines due to blade appearance in schematics.

Final Answer:
the water enters at the outer periphery and then flows towards the centre