Author(s): Junq Iang Lin; Nan Jing; Ch Ina; Zhongmin Yan; Jihong Xia; Nan Jing; Ch Ina
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Keywords: Numerical models; Pres s u re fields; Near-bank; VOF method; Rig id lid method
Abstract: The in teract ion between f low and riverbank mo rpho logy res u lts in a local p res s u re g rad ien t on the bank s u rface wh ich leads to lateral hypo rheic e xchange. The latera l hypo r heic e xchange p lays an impo rtan t ro le in r iver ecos ys tem. It enhances b iogeochemica l trans fo rmat ions in the riverbank that may in f luence bo th su rface and s ubs u rface water qual ity, r iver metabo lis m, fate and up take o f con taminan ts. The s imu lat ion and p red ic t ion o f p res s u re d is tribu t ion along the bank is the impo rtan t p rerequ is ite fo r the s tudy on lateral hypo rheic exchange, con taminan t trans po rt and the circu lat ion o f eco log ical ly relevan t s ubstances between rivers and riparian zones. Two 3D nume rica l models us ing d ifferen t free -s u rface treatmen ts (r ig id lid method and vo lume o f f lu id (VOF) method) have been developed fo r s imu lat ing f low and near-bank p res su re field induced by s inuous bank mo rpho logy. The flo w is calcu lated by s o lv ing the Reyno lds -averaged Nav ier–Stokes equat ions with the RNG k -ε tu rbu lence mode l. The f low equat ions are s o lved numer ical ly w ith a fin ite -vo lu me method on s tructu red hexahed ron g rids. A s et o f labo rato ry e xperimen ts with d ifferen t bank s inuos it ies and d ifferen t in let velocit ies ar e p res en ted to test the numer ical models. The co mpar is ons o f s imu lated near -bank p res s u re p ro files and the meas u re men ts ind icate that bo th models can p red ict the p res s u re d is tribu t ion we l l a long the bank when the Froude number and bank s inuos ity are re lat ive ly low. The model bas ed on rig id l id method is mo re compu tat ionally ef f icien t than the model bas ed on VOF method. W hen the Froude number and bank s inuos ity are relat ively h igh, the VOF method can imp rove the p red ict ions fo r the p res s u re d is tribu t ion. With the increas ing o f Froude number and bank s inuos ity, the imp rove men t o f p res s u re p red ict ion by VOF method is become mo re apparen t than the rig id lid method.
Year: 2013