Evolution of Scour and Velocity Fluctuations Due to Turbulence Around Cylinders

Experimental investigation of the impacts of coherent flow structures upon turbulence properties in regions of crescentic scour

“…Formation of scour marks upstream of the cylinder showed a crescentic scour structure, which is morphologically akin to the current crescent preserved in geological record (Sengupta, , ). During the process of evolution of scour marks at the upstream edge due to blockage in the flow, the geometry of the structure was recorded at an approximately equal interval of time using a digital camera (Mazumder et al ., ; Maity et al ., ). It may be noted that two basic forms of erosion took place around obstacles − bluff erosion, which occurred at the upstream side of the obstacle caused by an eddy formation; and lee erosion occurred at the downstream side of the obstacle with turbulent wakes at the both ends.…”

“…Subsequently, Maity et al . () developed a statistical model for spatio‐temporal evolution of scour width around short cylinders due to fluid flows.…”

“…Extensive investigations relevant to a variety of scientific disciplines have been made over the last few decades in laboratory settings under controlled conditions on the scour holes around vertical cylinders or piers embedded in sediment beds (Melville, 1975;Melville and Raudkivi, 1977;Raudkivi and Ettema, 1983;Darghai, 1989;Melville and Chiew, 1999;Graf and Istiarto, 2002;Sheppard et al, 2004;Ettema et al, 2006;Unger and Hager, 2007;Debnath et al, 2012), underwater pipelines Fredsoe, 2002a, 2002b) and around abutments (Kwan and Melville, 1994;Ahmed and Rajaratnam, 2000;Dey and Barbhuiya, 2005;Dey et al, 2008). Local scour around short/finite horizontal cylinders placed in non-cohesive sediment beds have also been investigated (Voropayev et al, 1999(Voropayev et al, , 2003Sengupta et al, 2005;Garcia, 2006, 2007;Mazumder et al, 2011, Maity et al, 2013.…”

“…They apparently showed that for a fixed value of F s ranging from 3.5 to 6.0, dimensionless scour-width ws L À Á increases with increase of R cyl ; and proposed a relation for dimensionless scour-width ws L À Á as a function of D c and F s , where w s is the width of the scour hole. Subsequently, Maity et al (2013) developed a statistical model for spatio-temporal evolution of scour width around short cylinders due to fluid flows.…”

Prediction of plane‐wise turbulent events to the Reynolds stress in a flow over scour‐bed

“…It hitherto remains unclear whether the statistical properties of all three covariance terms, , , and are equally important over the scour hole structure or there is one leading shear stress plane out of the three involving the bursting events over and within the scour geometry to be investigated. The development of scour mark around the obstacle on the sandy bed under the action of turbulent flow has the potential to be useful to researchers or scientists who study the dynamics of pipelines and short cylinders placed on riverbeds, seabeds, and coastal areas (Sumer & Fredsoe, , ; Voropayev, Cense, McEachern, Boyer, & Fernando, ; Voropayev, Testik, Fernando, & Boyer, ); the flow field around bridge piers (Melville & Raudkivi, ); and the development of crescentic scour marks in a recent stream (Bhattacharya, ; Maity, Dasgupta, & Mazumder, ; Sarkar, et al, , ; Sengupta, , ) for prediction of palaeocurrent directions.…”