Kevin Bobiles

Flow dynamics over estuarine bedforms

In many tide-dom­in­ated en­vir­on­ments, sandy sed­i­ments are be­ing mo­bil­ized to de­velop un­du­la­tions and rhythmic wavy fea­tures, col­lect­ively known as bed­forms. An in-depth study of their mor­pho­logy that in­cludes, but is not lim­ited to, their pres­ence, size and move­ment is im­port­ant in pre­dict­ing an ac­cur­ate hy­dro-morpho­dy­namic re­sponse of the sur­round­ing en­vir­on­ment at vari­ous spa­ti­otem­poral scales. This is in turn an im­port­ant as­pect to many prac­tical and en­gin­eer­ing ap­plic­a­tions such as coastal zone man­age­ments, port and chan­nel main­ten­ance. 

Pre­vi­ous stud­ies have char­ac­ter­ised flow over tri­an­gu­lar bed­forms with an angle-of-re­pose (30°) lee side. However, the shape and dy­nam­ics of es­tu­ar­ine bed­forms dif­fers sig­ni­fic­antly to that of angle-of-re­pose dunes, as they are mainly low- to in­ter­me­di­ate-angle dunes (slopes of 5 to 20°) with a sharp poin­ted crest. Flow prop­er­ties for this par­tic­u­lar bed­form mor­pho­logy and the re­vers­ing tidal flow present in an es­tu­ar­ine en­vir­on­ment have not been in­vest­ig­ated in de­tail.

There­fore, the main ob­ject­ive of my PhD pro­ject is to study and in de­tail the flow dy­nam­ics (flow ve­lo­cit­ies, tur­bu­lent struc­tures, etc.) over es­tu­ar­ine bed­forms through a com­bin­a­tion of phys­ical ex­per­i­ments and nu­mer­ical mod­el­ling. A series of large-scale flume ex­per­i­ments will be con­duc­ted at  BAW Ham­burg to study 2D es­tu­ar­ine bed­form fields whose modeled shapes are based on meas­ure­ments ob­tained in the Weser Es­tu­ary. Fi­nally, nu­mer­ical mod­el­ing of flow dy­nam­ics over 3D nat­ural bed­form fields will com­ple­ment the flume ex­per­i­ments. To­gether, the res­ults of both labor­at­ory and nu­mer­ical stud­ies will al­low us to char­ac­ter­ise in de­tail the flow struc­tures over es­tu­ar­ine bed­forms and en­able bet­ter para­met­erisa­tion of small scale pro­cesses into large scale hy­dro-morpho­dy­namic mod­els.