M. Salamatian, A. R. Zarrati, S. A. Zokaei, M. Karimaee,
Volume 11, Issue 3 (9-2013)
Abstract
The efficiency of a collar in reducing the scour depth around circular and rectangular piers is studied at different flow intensities (ratio of upstream shear stress to sediment critical shear stress). Rectangular Piers aligned with the flow as well as skewed at 5º, 10º, 20º were examined. Previous studies had shown that with collar the equilibrium time of scouring increases considerably. To reduce the time of experiments low density sediment was used as the bed materials. Comparison between test results and available results with natural sediment showed that, though the relative equilibrium depths were approximately similar, the time to reach equilibrium condition diminished to less than 10 hours with low density sediment. Experimental results for circular and aligned rectangular pier showed that at u*/u*c=0.95 to 0.75 the collar could reduce the maximum scour hole from about 20% to 60% respectively. In rectangular pier, by increasing the skew angle and/or the flow intensity, the efficiency of collar decreased.
Gholamhossein Akbari,
Volume 14, Issue 3 (4-2016)
Abstract
Abstract: Comprehensive computational analysis was made for modelling the integrated hydrologic- hydraulics characteristics of varied unsteady flow in hydraulic structures as part of water engineering practices and river basin management. Several numerical skills, linear, nonlinear, implicit, explicit methods were developed and tested with existing river analysis software of Danish Hydraulic Institute (DHI) and Hydrologic Engineering Centre (HEC) series models. Coupled hydrological and hydraulics analysis of storming run-off flows in broad waterways boundaries including flood plains of compound sections were studied. Application of models was encouraging, the complex water conveyance systems transported lateral flows in natural rivers were modelled satisfactorily. Storming flow events in real rivers were coded and compared through different numeral techniques such as Method of Characteristics, Mac-Cormack, Diffusive numeral model and Preissmann fully implicit model. Predicted results were close to observed values verified and confirmed the hand written codes and programs in MATLAB environment. Enhanced modelling skills were justified by (HEC) series and Mike series computer software. Merits of this research were seen based on numerical accuracy, consistency, stability and converging results to observed targets.
Mohammad Naghian, Mohsen Lashkarbolok, Ebrahim Jabbari,
Volume 15, Issue 1 (1-2017)
Abstract
A least squares based meshfree method is used in the numerical simulation of a turbulent flow. The proposed approach is integral free, vectorized and enjoying sparse positive definite matrices. Here the standard k-ε model is employed to model the turbulent flow. A matrix formulation is illustrated that simply can be extended for other turbulence models. Two bench mark problems are solved and results are compared with the literature.
Volume 15, Issue 7 (10-2017)
Abstract
In this paper, the scour hole dimensions around submerged and emerged spur dike in a 90o bend along with the mean and turbulent flowfield were investigated experimentally. Two types of re-circulating flow at the downstream of the spur dike and around the spur dike wing were observed. A direct relation between the estimated bed shear stress using TKE and the scour process prevails. More attentions is needed in estimating the bed shear stress using vertical velocity fluctuations. The scour hole dimensions increase by increasing the ratio of radius of channel bend to channel width , the Froude number of the spur dike, ratio of the length of spur dike to channel width and ratio of the approach mean flow velocity to the approach flow velocity at threshold condition. However, vice versa trends were observed by increasing ratio of the spur dike length to the median sediment size, ratio of the wing length of spur dike to the length of spur dike and the submergence ratio. A particular location of the spur dike in the sharp bend was specified beyond which the scour hole dimensions increase. The ratio of the spur dike length to the median sediment size has a secondary effect on the scour hole dimensions. New equations are proposed for prediction of the scour hole dimensions considering the submergence ratio along with other effective parameters.
