Date of Award
Master of Science in Engineering (MSE)
Mechanical and Aerospace Engineering
Robert A. Frederick Jr.
Judith A. Schneider
Cavitation., Manufacturing processes., Fluid mechanics.
Additive manufacturing is becoming prevalent in the field of fluids and flow control with the advent of Selective Laser Sintering (SLS) and Selective Laser Melting (SLM). Due to the roughness of additively manufactured components, parts routinely need post-machining to reduce surface roughness and match the characteristics of subtractively manufactured components. This research aims to quantify the effects of layer-induced surface roughness on effective cross-sectional area reduction and cavitation onset conditions. Tests were performed on a 3/16” diameter, long length-to-diameter ratio (L/D = 20), sharp edged inlet orifice geometry using water at ambient temperature conditions. Tests were performed over a range of Cavitation Numbers, K, from K=1.6 to K=1.0. This was achieved by measuring pressure upstream of the venturi and controlling the backpressure applied. Upstream pressure was 500 psig with a programmable backpressure globe valve set to follow a setpoint schedule of Cavitation Numbers. This was to determine the effective area (Cc*A) as used in the Nurick model and the cavitation onset cavitation number (Kcrit) which will be compared between venturis with different manufacturing methods and therefore roughness. Arithmetic mean roughnesses ranging from 0.26 μm to 26.85 μm were tested using subtractive manufacturing techniques, Fused Deposition Modeling, and Selective Laser Melting. Results found shown an appreciable reduction in effective flow area with increasing roughness. Decreases in Cc of 12.3% from a smooth bore orifice to that of the roughest configuration tested were found. Additionally, delays in cavitation offset were observed with cavitation onset occurring at K=1.08 rather than the predicted K=1.45 for the roughest configuration tested.
Hicks, Robert Dalton, "Manufacturing effects on water cavitation in long L/D sharp edge inlet orifices" (2019). Theses. 301.