Effect of unsteady flow conditions on scour features at low-head hydraulic structures

The estimation of a river discharge by using a mean velocity equation is very convenient and rational. Nevertheless, a research on an equation calculating a mean velocity in a river was not entirely satisfactory after the development of Chezy and Mannings formulas which are uniform equations. In this paper, accordingly, the mean velocity in unsteady flow conditions which are shown loop form properties was estimated by using a new mean velocity formula derived from Chius 2-D velocity formula. The results showed that the proposed method was more accurate in estimating discharge, when compared with the conventional formulas.

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Computational Study of the Risø-B1-18 Airfoil with a Hinged Flap Providing Variable Trailing Edge Geometry

Wind Engineering ◽

10.1260/0309524054797159 ◽

2005 ◽

Vol 29 (2) ◽

pp. 89-113 ◽

Cited By ~ 61

Author(s):

Niels Troldborg

Keyword(s):

Reynolds Number ◽

Unsteady Flow ◽

Computational Study ◽

Turbine Blades ◽

Aerodynamic Characteristics ◽

Flow Conditions ◽

Wind Turbine Blades ◽

Trailing Edge ◽

Edge Geometry ◽

Fully Developed Turbulent Flow

A comprehensive computational study, in both steady and unsteady flow conditions, has been carried out to investigate the aerodynamic characteristics of the Risø-B1-18 airfoil equipped with variable trailing edge geometry as produced by a hinged flap. The function of such flaps should be to decrease fatigue-inducing oscillations on the blades. The computations were conducted using a 2D incompressible RANS solver with a k-w turbulence model under the assumption of a fully developed turbulent flow. The investigations were conducted at a Reynolds number of Re = 1.6 · 106. Calculations conducted on the baseline airfoil showed excellent agreement with measurements on the same airfoil with the same specified conditions. Furthermore, a more widespread comparison with an advanced potential theory code is presented. The influence of various key parameters, such as flap shape, flap size and oscillating frequencies, was investigated so that an optimum design can be suggested for application with wind turbine blades. It is concluded that a moderately curved flap with flap chord to airfoil curve ratio between 0.05 and 0.10 would be an optimum choice.

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Competitive flow and anastomosis angle influence on bypass hemodynamics in unsteady flow conditions

10.1063/1.4992166 ◽

2017 ◽

Cited By ~ 3

Author(s):

A. F. Totorean ◽

S. I. Bernad ◽

I. C. Hudrea ◽

R. F. Susan-Resiga

Keyword(s):

Unsteady Flow ◽

Flow Conditions

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Additional Developments of the Optical Pressure Measurement System (OPMS) for Non-flat Models and Unsteady Flow Conditions

International Congress on Instrumentation in Aerospace Simulation Facilities, ◽

10.1109/iciasf.1993.687693 ◽

2005 ◽

Author(s):

R.H. Engler

Keyword(s):

Unsteady Flow ◽

Measurement System ◽

Pressure Measurement ◽

Flow Conditions ◽

Optical Pressure ◽

Pressure Measurement System

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Modification of Classical Horseshoe Spillways: Experimental Study and Design Optimization

Civil Engineering Journal ◽

10.28991/cej-2019-03091396 ◽

2019 ◽

Vol 5 (10) ◽

pp. 2093-2109

Author(s):

Vahid Hassanzadeh Vayghan ◽

Ali Saber ◽

Soroosh Mortazavian

Keyword(s):

Hydraulic Jump ◽

Design Parameters ◽

Hydraulic Structures ◽

Flow Conditions ◽

Design Factor ◽

Flow Passage ◽

Water Head ◽

Cubic Polynomial ◽

Polynomial Models ◽

Discharge Efficiency

Investigation of the hydraulic aspects of spillways is one of the important issues regarding hydraulic structures. This study presents a modified horseshoe spillway (MHS) constructed by adding a flow passage and an internal weir in the bed of a classical horseshoe spillway (CHS). This modification increased the discharge efficiency and eliminated the rooster-tail hydraulic jump in CHSs. Eighteen laboratory-scale MHSs in various geometric sizes, six various CHSs, and a rectangular weir of the same width were constructed and tested under the same flow conditions. Results showed that in terms of discharge efficiency and water head reduction, CHSs and MHSs were superior to the rectangular weir. Compared to CHSs, the increased discharge flowrate in MHSs due to the internal weirs could further reduce the water head and thus increased their overall efficiencies. Design parameters effecting spillways’ discharge efficiencies were investigated based on dimensional analysis. The internal to external weir length ratio in MHSs was found to be a key design factor. To determine the optimal geometric design of CHS and MHS models, cubic polynomial models considering dimensionless parameters and their interactions were fitted to the experimental results. The cubic models revealed that higher discharge efficiencies in MHSs tended to occur at relatively low water heads and high internal to external weir lengths ratios.

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Numerical hydrodynamic researches for justifying design of the Nizhny Novgorod low-head hydraulic system

Stroitel stvo nauka i obrazovanie [Construction Science and Education] ◽

10.22227/2305-5502.2019.2.3 ◽

2019 ◽

pp. 3-3

Author(s):

Anna Glotko ◽

Vitalii Belikov ◽

Natalia Borisova ◽

Ekaterina Vasil`eva ◽

Aleksey Rumjancev

Keyword(s):

Numerical Methods ◽

Hydraulic System ◽

Problem Area ◽

Low Flow ◽

Hydroelectric Power Station ◽

Two Dimensional ◽

Hydroelectric Power ◽

Flow Conditions ◽

Power Station ◽

Low Head

Introduction. A problem area of the Volga river between the Nizhny Novgorod hydroelectric power station and the city of Nizhny Novgorod has been surveyed, where unfavourable conditions for navigation, power generation, and safe living in the downstream are formed as a result of the landing level. The only solution to the problem is construction of a low-head hydraulic system (NNGU) that will reduce intensity of relief re-formations in the downstream of the Nizhny Novgorod hydraulic system and stop lowering of the bottom and level marks in this area. Purpose of this research is to study processes that occur upstream and downstream from the site of the facility to identify hazardous trends and develop practical solutions to minimize negative impacts; as well as a review of mathematical models conducted in this area for improving navigation conditions. Materials and methods. Materials of previous researches on this subject, pre-design engineering surveys and layout drawings of the designed hydraulic system are used. The researches have been performed with numerical methods using Stream 2D software package that is based on the two-dimensional differential equation Saint-Venant system. Options for low-flow conditions are considered, taking into account passing of the Nizhny Novgorod hydroelectric power station, as well as rare floods. Results. Plans for distribution of velocity modules and vectors are created, which show that construction of the low-pressure hydraulic system results in decrease in slopes and velocities of water in the problem area of the Volga-Kama cascade, as a result of which intensity of bottom deformations decreases. Rare flow passage demonstrated that difference in pools is insignificant, while, at the same time, flow of water along the left-bank floodplain passes more than believed before. Calculations of low-flow conditions demonstrated a number of deficiencies in the design, which are associated with insufficient throughput and uneven distribution of flow rates in the discharge area of the waterfront. Conclusion The results demonstrated a practical importance of using mathematical simulation with numerical methods in a two-dimensional formulation, which allow us to consider processes in more detailed manner and change the hydraulic system design in a timely manner.

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