Abstract
This paper reports flow visualisation studies on a sphere of 250 mm dia. for both stationary and rotating cases with jet flow and rotating sphere without jet. Nozzle of 10 mm dia was used. China Clay technique was adopted to visualize the flow pattern. The studies have been carried out by varying the following three quantities (1) Jet Reynolds numbers (2) Ratios of gapheight to nozzle dia (h/D ratios) and (3) rotational Reynolds numbers. Experiments were also conducted with trip wires of different cross sectional areas and different sizes of the rings to precipitate transition to turbulence for sphere rotating in stationary ambient. Attempts are made to prevent the flow from bottom hemisphere by placing different sizes of circular discs below it, for sphere rotating in stagnant ambient. Photographs were taken for all the cases.
Results in the case of sphere rotating in stagnant air reveal good confirmations of previous results. Results in other cases are with the ultimate exposure of qualitative indications of nature of flow. Increasing jet Reynolds numbers and decreasing h/D ratios increase the stagnation zone in the impingement region. Under the conditions of study, flow is found to be turbulent in all the cases with jet. Changes in jet Reynolds numbers and decreasing h/D ratios increase the stagnation zone in the impingement region. Under the conditions of study, flow is found to be turbulent in all the case with jet. Changes in jet Reynolds numbers and h/D ratios have least effect on the nature of flow. Rotation has a marked effect on the flow pattern and hints at the presence of possible embedded vertices in certain cases of rotation.
