Colorado State University
Computational fluid dynamics models of Rio Grande bends fitted with rock vanes or bendway weirs.
Degree: MS(M.S.), Civil and Environmental Engineering, 2019, Colorado State University
Rock vanes (also known as stream barbs) and bendway weirs are two types of transverse rock structures used to modify the flow field in river bends. This study examines the effectiveness of the two types of structures at reducing velocity along the outer bank of river bends to protect the bank from erosion. A numerical model using the commercially available FLOW-3D software was used to evaluate the effect of various rock vane and bendway weir configurations on the flow field through two river bends typical of the Middle Rio Grande. The model was calibrated and validated using data from a previous physical model study of rock vanes. 33 different rock vane configurations were tested in the numerical model to evaluate the effect of altering planform angle, crest slope, projected length, and structure spacing. In addition, 14 different bendway weir configurations were tested to provide a comparison of the relative performance of bendway weirs and rock vanes. The numerical modeling results indicate that rock vanes are more effective at reducing the velocity along the outer bank of a bend than bendway weirs. Modelling showed that the completely submerged crest of bendway weirs allows a substantial amount of flow to pass over the crest, limiting their effectiveness in reducing velocity along the bank. In contrast, rock vanes, with a sloped crest intersecting the waterline at the design flow rate, directed more flow around the tip of the structure rather than over the crest and were much more effective at reducing velocity along the bank. Based on the modeling results, it is recommended that bendway weirs not be installed for the purpose of erosion protection along riverbanks. The reduction in velocity along the bank produced by the various rock vane configurations varied considerably with the geometry of the configuration. Based on the results, the following conclusions are made regarding rock vane geometry: (1) Rock vanes should be installed at a planform angle between 45° and 90° to the river bank. (2) There exists an optimal projected length of rock vane, which lies in the neighborhood of 1/5 to 1/3 of the channel top-width. (3) Rock vanes with a 10% crest slope perform well, although decreasing the crest slope will decrease the velocity along the outer bank and vice versa. (4) Decreasing the spacing of rock vanes decreases the velocity along the outer bank, up to a limit. A design equation was developed to predict the velocity reduction along the bank of a river bend produced by a given configuration of rock vanes, based on the geometry of the rock vanes and the river channel. The equation provided good predictions for the range of configurations tested, having a coefficient of determination r2 = 0.83 and predicting the velocity reduction along the outer bank to within 15 percentage points for all of the tested configurations.
Advisors/Committee Members: Ettema, Robert (advisor), Thornton, Christopher (committee member), McGrath, Daniel (committee member).
Subjects/Keywords: bendway weirs; erosion protection; stream barbs; computational fluid dynamics; bank stabilization; rock vanes
to Zotero / EndNote / Reference
APA (6th Edition):
Siefken, S. (2019). Computational fluid dynamics models of Rio Grande bends fitted with rock vanes or bendway weirs. (Masters Thesis). Colorado State University. Retrieved from http://hdl.handle.net/10217/197259
Chicago Manual of Style (16th Edition):
Siefken, Seth. “Computational fluid dynamics models of Rio Grande bends fitted with rock vanes or bendway weirs.” 2019. Masters Thesis, Colorado State University. Accessed April 12, 2021.
MLA Handbook (7th Edition):
Siefken, Seth. “Computational fluid dynamics models of Rio Grande bends fitted with rock vanes or bendway weirs.” 2019. Web. 12 Apr 2021.
Siefken S. Computational fluid dynamics models of Rio Grande bends fitted with rock vanes or bendway weirs. [Internet] [Masters thesis]. Colorado State University; 2019. [cited 2021 Apr 12].
Available from: http://hdl.handle.net/10217/197259.
Council of Science Editors:
Siefken S. Computational fluid dynamics models of Rio Grande bends fitted with rock vanes or bendway weirs. [Masters Thesis]. Colorado State University; 2019. Available from: http://hdl.handle.net/10217/197259