The Effect of surface scalloping on flow hydrodynamics and pressure drop

Abstract

Scalloping, a texturing of a corroding surface that imparts the appearance of orange peel, is commonly observes in the area exposed to the flow assisted-corrosion. the effects of surface scalloping on flow hydrodynamics and pressure drop remain unclear. the scalloped surface characteristics are believed to be mainly a function of flow hydrodynamics. on the other hand, the special surface characteristics of the scallop are also believed to change the hydrodynamics which affects the pressure drop. in this thesis, two dimensional (2d) scalloped surface was studied. the experiments were conducted in an atmospheric-pressure, recirculating loop. the internal surface of the acrylic test section was machined into scalloped surfaces. static pressure was measured along the test section with various Reynolds numbers of flow. flow separation causing flow recirculation was observed in congruence with a previous study. flow hydrodynamics simulated by CFD code – Fluent 6.3.26 was validated with the experimental results and SST k-ω is the most appropriate viscous model. it was found that the pressure drop of 2d scalloped surface was proportional to its surface area but was not a function of scalloped distribution. the von Karman equation for fully roughness in turbulence flow cannot be used to predict the friction factor for the scalloped surface accurately and the values of friction factor obtained from backward and forward flows on the scalloped surface were unidentical even though the roughness was the same.