Mehrdad Raisee
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View article: On the effect of draft tube rod protrusion on runner blade stress fatigue of single-regulated axial turbines
On the effect of draft tube rod protrusion on runner blade stress fatigue of single-regulated axial turbines Open
Under off-design and transient operations of hydraulic turbines, these machines are subjected to harmful pressure fluctuations originating from the presence of vortical flow. These oscillations increase stress-induced fatigue damage on the…
View article: Bi-fidelity adaptive sparse reconstruction of polynomial chaos using Bayesiancompressive sensing
Bi-fidelity adaptive sparse reconstruction of polynomial chaos using Bayesiancompressive sensing Open
In recent years, non-intrusive polynomial chaos expansion (NIPCE) has been known as a practical method for uncertainty quantification (UQ) of stochastic problems. However, this method suffers from the curse of dimensionality, such that the…
View article: Extending the operating range of axial turbines with the protrusion of radially adjustable flat plates: An experimental investigation
Extending the operating range of axial turbines with the protrusion of radially adjustable flat plates: An experimental investigation Open
The implementation of hydropower to stabilize electrical grids dictates more frequent off-design operations of these renewable energy resources. Flow instabilities under such conditions reduce the efficiency of hydro turbines. Part-load op…
View article: The effects of balancing holes on the axial force of a centrifugal pump in the reverse mode
The effects of balancing holes on the axial force of a centrifugal pump in the reverse mode Open
Centrifugal pumps can feasibly act as turbines in small hydropower plants. However, prediction and reduction methods of axial force is still challenging. A proposed method to this goal is the use of balancing holes. Accordingly, this paper…
View article: Numerical investigation of axial force of a centrifugal pump in the reverse mode
Numerical investigation of axial force of a centrifugal pump in the reverse mode Open
This paper numerically investigates the hydraulic performance and axial force of a low specific speed centrifugal pump in the turbine mode using the k - ω SST model. Numerical results are validated against the experimental data in the lite…
View article: Numerical investigation of hydrodynamic damping of a pitching hydrofoil at different flow regimes
Numerical investigation of hydrodynamic damping of a pitching hydrofoil at different flow regimes Open
Due to the development of intermittent renewable energy resources, hydropower plants are mostly operated under off-design conditions. This may lead to natural frequency excitation shortening the turbine life-span. To accurately estimate th…
View article: Experimental Investigation of Part Load Vortex Rope Mitigation With Rod Protrusion in an Axial Turbine
Experimental Investigation of Part Load Vortex Rope Mitigation With Rod Protrusion in an Axial Turbine Open
The present paper investigates the rotating vortex rope (RVR) mitigation on an axial turbine model by the radial protrusion of four cylindrical rods into the draft tube. RVR mitigation is of particular interest due to the unfavorable press…
View article: Optimal flow control of vortex breakdown in a laminar swirling flow
Optimal flow control of vortex breakdown in a laminar swirling flow Open
In highly swirling flows, such as hydraulic turbines operating under part-load (PL) conditions, vortex breakdown occurs and performance is impaired. Consequently, it is imperative that mitigation measures are taken. In the present study, a…
View article: Experimental investigation of an adjustable guide vane system in a Francis turbine draft tube at part load operation
Experimental investigation of an adjustable guide vane system in a Francis turbine draft tube at part load operation Open
Hydraulic turbines are increasingly used to regulate the electrical grid. They thus have to operate more often at off-design conditions where instabilities may develop leading to large pressure pulsations decreasing the life of the machine…
View article: Hydraulic Performance of a Francis Turbine with a Variable Draft Tube Guide Vane System to Mitigate Pressure Pulsations
Hydraulic Performance of a Francis Turbine with a Variable Draft Tube Guide Vane System to Mitigate Pressure Pulsations Open
The present paper demonstrates a proof-of-concept by introducing a variable guide vane system in the draft tube of a high-head Francis model turbine. The aim is to examine the hydraulic performance of the turbine while mitigating the press…
View article: An experimental investigation on the effects of cylindrical rods in a draft tube at part load operation in down-scale turbine
An experimental investigation on the effects of cylindrical rods in a draft tube at part load operation in down-scale turbine Open
The present work examines the effects of the radial protrusion of four cylindrical rods at different lengths within the flow field of a down-scaled turbine draft tube under part-load operating conditions. Four rods were placed on the same …
View article: Draft tube guide vane system to mitigate pressure pulsations
Draft tube guide vane system to mitigate pressure pulsations Open
The present study introduces the concept of mitigating pressure pulsations in a hydro-turbine draft tube. The concept refers to using an adjustable guide vane system in the draft tube. The adjustability relates to its ability to rotate aro…
View article: PIV measurements in the draft tube of a down-scale propeller turbine: uncertainty analysis
PIV measurements in the draft tube of a down-scale propeller turbine: uncertainty analysis Open
In this study, the flow in the conical section of the draft tube of a propeller turbine has been investigated at the best efficiency point and part-load operating conditions using 2D and stereoscopic 3D particle image velocimetry. Since th…
View article: A Novel Guide Vane System Design to Mitigate Rotating Vortex Rope in High Head Francis Model Turbine
A Novel Guide Vane System Design to Mitigate Rotating Vortex Rope in High Head Francis Model Turbine Open
Guide vanes are a mechanical system used to direct flow in the desired direction. At lower operating conditions, implementing a guide vane system in the draft tube of a hydro-turbine can decrease the excess swirl in the flow and, thus, red…
View article: Velocity Measurements in Kaplan and Propeller Turbines: a review
Velocity Measurements in Kaplan and Propeller Turbines: a review Open
Complex geometry and flow regimes are present in different sections of hydraulic turbines and most operating conditions. In the past two decades, many pressure measurements have been performed on different sections. Such measurements do no…
View article: Mitigation of Draft Tube Pressure Pulsations by Radial Protrusion of Solid Bodies into the Flow Field: An Experimental Investigation
Mitigation of Draft Tube Pressure Pulsations by Radial Protrusion of Solid Bodies into the Flow Field: An Experimental Investigation Open
An experimental investigation of frequential protrusion of four solid rods into the draft tube of a propeller turbine operating under partial discharge has been undertaken. The effectiveness of mitigating the pressure fluctuations associat…
View article: Study of Flow Characteristics inside Francis Turbine Draft Tube with Adjustable Guide Vanes
Study of Flow Characteristics inside Francis Turbine Draft Tube with Adjustable Guide Vanes Open
Numerical investigation was performed on a semi-model (one stay vane, two guide vanes, one runner passage inclusive of one main and one splitter blade, and the draft tube) of a high-head Francis turbine model with adjustable guide vanes in…
View article: Reduced Numerical Modeling of a High Head Francis Turbine Draft Tube at Part Load
Reduced Numerical Modeling of a High Head Francis Turbine Draft Tube at Part Load Open
In the present study, a reduced model of the Francis-99 model turbine was investigated numerically at part load operating condition. The reduced model consists of a standalone draft tube domain of the Francis-99 model turbine. Numerical st…
View article: The effect of balancing holes on performance of a centrifugal pump: numerical and experimental investigations
The effect of balancing holes on performance of a centrifugal pump: numerical and experimental investigations Open
In the present work, the effect of balancing hole's diameter on the performance of a centrifugal pump is experimentally and numerically investigated. Normally, in centrifugal pumps, design of impeller and volute is carried out in such a wa…
View article: Numerical investigation of tongue effects on pump performance in direct and reverse modes
Numerical investigation of tongue effects on pump performance in direct and reverse modes Open
This paper investigates the effects of tongue geometry on the performance and radial force of a low specific speed centrifugal pump in direct and reverse modes numerically. For the evaluation of unknown Reynolds stresses, the k-ω turbulenc…
View article: Numerical investigation of tip leakage vortex cavitation
Numerical investigation of tip leakage vortex cavitation Open
Tip leakage vortex cavitation is a concern for axial hydraulic turbines. Generally, cavitation may occur in the core of the TLV, often leading to erosion of the runner blades and the casing. The objective of this paper is to study the effe…
View article: A novel volute design for reducing radial force in pump and PAT
A novel volute design for reducing radial force in pump and PAT Open
In the current paper a novel volute design is proposed to reduce the radial force of a low specific speed centrifugal pump in both direct and reverse modes. First, the fluid flow in the pump in both modes was simulated by utilizing commerc…
View article: Effects of Upstream Flow Conditions on Runner Pressure Fluctuations
Effects of Upstream Flow Conditions on Runner Pressure Fluctuations Open
The rotor-stator interaction and the corresponding pressure fluctuations represent one of the sources of pressure and load fluctuations on the rotating parts of rotating machineries. The high-Reynolds flow is subject to rotation in the com…
View article: Computation of Developing Turbulent Flow through a Straight Asymmetric Diffuser with Moderate Adverse Pressure Gradient
Computation of Developing Turbulent Flow through a Straight Asymmetric Diffuser with Moderate Adverse Pressure Gradient Open
In this paper, numerical investigation of three-dimensional, developing turbulent flow, subjected to a moderate adverse pressure gradient, has been investigated using various turbulence models, namely: the low-Re , the SST , the and a vari…