Khalid M. Saqr

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Verified

Khalid verified their affiliation via an institutional email.

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• Ph.D.
• Faculty Member at Arab Academy for Science, Technology, and Maritime Transport

Contemporary paradigm of peripheral and intracranial vascular hemodynamics considers physiologic blood flow to be laminar. Transition to turbulence is considered as a driving factor for numerous diseases such as atherosclerosis, stenosis and aneurysm. Recently, turbulent flow patterns were detected in intracranial aneurysm at Reynolds number below...

The hemodynamics of intracranial aneurysm (IA) comprise complex phenomena that influence the IA’s growth and rupture risk. It has long been argued in in silico studies of IA hemodynamics that wall compliance could be neglected, because it does not alter the hemodynamic patterns. The purpose of this work is to investigate the effect of wall complian...

Despite the plethora of published studies on intracranial aneurysms (IAs) hemodynamic using computational fluid dynamics (CFD), limited progress has been made towards understanding the complex physics and biology underlying IA pathophysiology. Guided by 1733 published papers, we review and discuss the contemporary IA hemodynamics paradigm establish...

Endothelial cells (ECs) respond to flow stress via a variety of mechanisms, leading to various intracellular responses that can modulate the vessel wall and lead to diseases if the flow is disturbed. Mechano-microRNAs (miRNAs) are a subset of miRNAs in the ECs that are flow responsive. Mechano-miRNAs were shown to be related to atherosclerosis path...

Moyamoya disease (MMD) is a rare cerebro-occlusive disease with unknown etiology that can cause both ischemic and hemorrhagic stroke. MMD is characterized by progressive stenosis of the terminal internal carotid artery (ICA) and development of basal brain collaterals. Early-stage MMD is known to cause hemodynamic insufficiency despite mild or moder...

The symbolic architecture of non-ordinary consciousness remains largely unmapped in cognitive science and artificial intelligence. While conventional models prioritize rational coherence, altered states such as those induced by psychedelics reveal distinct symbolic regimes characterized by recursive metaphor, ego dissolution, and semantic destabili...

This work presents an analytical and theoretical investigation of the Gromeka acceleration field in a dimensionless Womersley flow, derived through the exact solution of the governing Navier-Stokes equations in phase space. By decomposing the convective acceleration into rotational and nonrotational components, the derivation highlights the dominan...

Large language models (LLMs) are reshaping information consumption and influencing public discourse, raising concerns over their role in narrative control and polarization. This study applies Wittgenstein’s theory of language games to analyze worldviews embedded in responses from four LLMs. Surface analysis revealed minimal variability in semantic...

Large language models (LLMs) are reshaping information consumption and influencing public discourse, raising concerns about their potential to empower narrative control and amplify polarisation. This study examines the embedded worldviews of four LLMs across key themes using Wittgenstein’s theory of language games to interpret meaning and narrative...

"Innovation Fast Forward offers academic researchers, managers, investors, entrepreneurs, and the general public an important framework to help understand the issues surrounding innovation." So writes Ayman S. Ashour in the Foreword of Khalid Saqr's vital new guide to innovation management. With insightful analysis and real-world case studies, Saqr...

In today’s $75 trillion global knowledge-economy, the world's 17 million faculty members, academic researchers, and scientists who are creating new knowledge capital and safeguarding existing knowledge should be rich and in control! Are you an academic striving for adequate rewards for your invaluable contributions to the global knowledge-economy?...

The study of turbulence in physiologic blood flow is important due to its strong relevance to endothelial mechanobiology and vascular disease. Recently, Saqr et al. (Sci Rep 10, 15,492, 2020) discovered non-Kolmogorov turbulence in physiologic blood flow in vivo, traced its origins to the Navier–Stokes equation and demonstrated some of its properti...

The study of turbulence in physiologic blood flow is important due to its strong relevance to endothelial mechanobiology and vascular disease. Recently, Saqr et al (Sci. Rep. 10, 15492, 2020) discovered non-Kolmogorov turbulence in physiologic blood flow in vivo, traced its origins to the Navier-Stokes equation and demonstrated some of its properti...

The mechanisms underlying the growth and rupture of aneurysms are poorly understood. Although the wall shear stress (WSS) in elastic aneurysm models is examined using fluid-structure interaction (FSI) simulations, it has not been sufficiently validated using experimental modalities, such as particle image velocimetry (PIV) or phase contrast magneti...

While doing daily physiological activities, the trabecular bone will experience a certain amount of deformation which leads to the bone marrow movement. The movement can affect the bone remodelling process and the properties of the bone itself. The bone marrow plays a role as a hydraulic stiffening of the trabecular structure. However, previous stu...

Endovascular stents have become a standard management procedure for carotid artery stenosis. Recent discoveries related to the complex turbulence dynamics in blood flow necessitate revisiting the pathology of carotid stenosis itself and the impact of stenting on blood hemodynamics. In the present work, and for the first time, the therapeutic hemody...

The complex physics and biology underlying intracranial hemodynamics are yet to be fully revealed. A fully resolved direct numerical simulation (DNS) study has been performed to identify the intrinsic flow dynamics in an idealized carotid bifurcation model. To shed the light on the significance of considering blood shear-thinning properties, the po...

There is an overwhelming evidence on SARS-CoV-2 Airborne Transmission (AT) in the ongoing COVID-19 outbreak. It is extraordinarily difficult, however, to deduce a generalized quantitative framework to assess the relative airborne transmission risk with respect to other transmission modes. This is due to the complex biophysics entailed in such pheno...

In arid regions, such as the North African desert, sandstorms impose considerable restrictions on horizontal axis wind turbines (HAWTs), which have not been thoroughly investigated. This paper examines the effects of debris flow on the power generation of the HAWT. Computational Fluid Dynamics (CFD) models were established and validated to provide...

Cerebral aneurysm is a fatal neurovascular disorder. Computational fluid dynamics simulation of aneurysm haemodynamics is one of the most important research tools which provide increasing potential for clinical applications. However, computational fluid dynamics modelling of such delicate neurovascular disorder involves physical complexities that c...

The purpose of this brief paper is to obtain quantitative information on mean velocity profile in ideal vasculature (i.e. straight and toroidal pipes) at low to medium shear rates. To shed the light on the significance of considering blood shear-thinning properties, the power-law model is compared to the commonly used Newtonian viscosity hypothesis...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Supplementary materials to "The hemodynamic complexities underlying transient ischemic attacks in early-stage Moyamoya disease: an exploratory CFD study"

Contemporary paradigm of vascular hemodynamics considers normal blood flow to be pulsatile laminar flow. Transition to turbulence can cause diseases such as atherosclerosis or brain aneurysms. However, recently we demonstrated the existence of turbulence in experimental models of brain aneurysm, in the aneurysm sac as well as in the main artery. Th...

Thomas Kuhn proposed his paradigmatic view of scientific discovery five decades ago. The concept of paradigm has not only explained the progress of science, but has also become the central epistemic concept among STM scientists. Here, we adopt the principles of Kuhnian philosophy to construct a novel ontology aims at classifying and evaluating the...

Computational Fluid Dynamics (CFD) has become an essential research tool to investigate the physical, biophysical and pathophysiological processes leading to the formation, growth and rupture of intracranial aneurysms (IAs). The diverse anatomical complexities of IAs dictate a staggering level of sophistication inherited in the CFD modeling process...

The genesis, growth and rupture of intracranial aneurysm (IA) are open questions in neurovascular medicine until the present moment. The complexity of aneurysm mechanobiology and pathobiology staggeringly combine intertwining biological and physical processes that are tightly connected. Recently, transition to turbulence in IA blood flow is thought...

The NACA HFSX hydrofoil is used in numerous renewable energy applications including marine current turbines (MCTs) which operate at relatively low Reynolds number (in this database Re=190,000). The flow around NACA HFSX hydrofoil at such Re value is transitional which makes the establishment of proper CFD models quite challenging. In the present wo...

Transition to turbulence in intracranial aneurysm (IA) is believed to contribute to the pathophysiological processes leading to aneurysm growth and rupture. In this work, comparative PIV measurements and LES computations are discussed to highlight some of the transitional features in an ideal side-wall saccular aneurysm. Kinetic energy cascade in d...

Nowadays, one of the major and serious worldly concerns is the limitation of energy resources. Sudan, in specific, confronts a critical crisis in fossil fuel resources due to its separation science 2011, and mostly concerning the production of electricity energy. There are many sources of renewable energies in Sudan such as hydropower. Which it is...

This short commentary argues that the use of vector notations with Wall Shear Stress in biofluid mechanics is inappropriate to represent biological and clinical features of vascular hemodynamics.

Computational fluid dynamics (CFD) studies of intracranial hemodynamics often use Newtonian viscosity model to close the shear rate term in the Navier-Stokes equation. This is based on a commonly accepted hypothesis which state that non-Newtonian effects can be neglected in intracranial blood flow. This study aims to examine the validity of such hy...

Invited Lecture at Computational Fluid Dynamics session of the 34th JSNET Annual Meeting.

In the present work, the effect of combustor geometry and inlet air velocity on flameless critical parameters such as recirculation ratio and mixing is investigated. The main objective is to develop evaluation criteria for flameless combustors design based on these critical parameters. A simple lab scale combustor with central air jet arrangement i...

Trapped vortex combustion, TVC, has shown promising results in terms of wide stability range and low pressure drop. However, previous experimental and numerical studies, which were limited to DNS, have provided only global performance assessments. Also, high computational cost limitations of DNS motivated the need for evaluating other lower cost tu...

Trapped vortex combustion, TVC, has shown promising results in terms of wide stability range and low pressure drop. However, previous experimental and numerical studies, which were limited to DNS, have provided only global performance assessments. Also, high computational cost limitations of DNS motivated the need for evaluating other lower cost tu...

Phase change materials (PCMs) have great potentials to be used in modern building materials to stabilize indoor temperature fluctuations for improving thermal comfort. This paper presents a comprehensive review on the use of PCMs in buildings to improve thermal comfort without increasing energy consumption. Concise discussions of the experimental a...

Gulf and South African countries have enormous potential for wind energy. However, the emergence of sand storms in this region postulates performance and reliability challenges on wind turbines. This study investigates the effects of debris flow on wind turbine blade performance. In this paper, two-dimensional incompressible Navier-Stokes equations...

The formation and growth of cerebral aneurysm (CA) involves numerous complex biological, biochemical and mechanobiological processes. Vascular endothelium is largely affected by hemodynamics. The response of endothelial cells (EC) to shear stress has been identified as the prime initiator of CA formation and growth. This paper presents a critical o...

The formation and growth of cerebral aneurysm (CA) involves numerous complex biological, biochemical and mechanobiological processes. Vascular endothelium is largely affected by hemodynamics. The response of endothelial cells (EC) to shear stress has been identified as the prime initiator of CA formation and growth. This paper presents a critical o...

Energy generation from marine currents is a promising technology for sustainable development. The success of using marine current turbines to tap the ocean hydrodynamic energy depends on predicting the hydrodynamic characteristics and performance of such turbines. This paper presents an analysis of the two dimensional flow using commercial CFD soft...

Partially open cavities are encountered in various engineering systems such as electronic cooling devices and cooling for gas turbine blades, instead of conventional film cooling slots. Flow is to be imparted over the partially open cavity where it induces a shear layer and a shear driven vortex within the cavity, which is subjected to cooling effe...

Recently, one of the major and serious worldly concerns is the limitation of energy resources. Sudan, in specific, confronts a critical crises relating to fossil fuel resources, and mostly concerning the production of electricity energy from fired thermal power plants. One of these Garri “2” combined cycle power plants produce about 180 MW. In the...

In this work, the passive flow control method was applied to improve the performance of symmetrical airfoil section in the stall regime. In addition to the commonly used first law analysis, the present study utilized an entropy generation minimization method to examine the impact of the flow control method on the entropy generation characteristics...

The wind turbine blades performance is strongly influenced by transitional separation bubbles, which may occur at low Reynolds numbers. Such a separation bubble is caused by a strong adverse pressure gradient, which makes the laminar boundary layer to separate from the curved airfoil surface. In the present paper, a CFD investigation is conducted t...

Sub-sea pipelines are affected with many surrounding challenges. One of these challenges is the current-induced hydrodynamic stresses which affect the pipeline throughout its life span. Therefore, several methods have been suggested to reduce these stresses and hence protect the pipe. The aim of this paper is to investigate the effect of one of the...

Extensive two dimensional (2D) numerical computations were conducted in the present work to both assess the ability of different RANS turbulence models to predict the flow physics of trapped vortices correctly, and to study the effect of both main stream Reynolds number and cavity length on the cavity flow structure. This study was conducted to pro...

Wind turbine blades work in variable surface roughness conditions during their operational life. The presence of surface roughness over the blade's surface generates a performance loss in the airfoil properties. Although there have been numerous studies on the similar effect of ice accumulation and rain in other climates, there has been quite a lim...

In the past 20 years, the use of wave energy systems has significantly increased, generally depending on the oscillating water column concept. Wells turbine is one of the most efficient oscillating water column technologies. This article provides an updated and a comprehensive account of the state-of-the-art research on Wells turbine. Hence, it dra...

Computational Fluid Dynamics (CFD) has become an emerging field in engineering since the early 1980s. The outbreak of personal computers during that era has revolutionized engineering practice in many industries and started a technology race between software companies to develop engineering analysis and simulation software for a wide range of appli...

This study investigates, analytically, the design of a new stand-alone agriculture Green House (GH) designed to be a self-sufficient of energy and irrigation requirements. This design uses Transparent Photo Voltaic (TPV) for electrical power generation and humidification-Dehumidification process for water production. The paper investigates the effe...

This paper presents a broad account of the lid-driven cavity flow problem which is an important benchmark problem for the validation of CFD codes. A comprehensive review of the literature on the problem is presented and discussed, and available benchmarking results are compared in tabulated format to provide a comprehensive source of validation dat...

Renewable energy is one of the main pillars of sustainable development, especially in developing economies. Increasing energy demand and the limitation of fossil fuel reserves make the use of renewable energy essential for sustainable development. Wind energy is considered to be one of the most important resources of renewable energy. In North Afri...

Hydrodynamic stress induced by marine currents subject subsea pipelines to failure vulnerability. Therefore, several methods have been established to protect such pipelines from hydrodynamic forces. The objective of this work is to investigate the performance of two different protection methods using computational fluid dynamics. A second-order acc...

This article extends the recent study by Saqr and Wahid (Applied Thermal Engineering 70 (2014) 486-493) on the criteria of heat transfer enhancement in swirl pipe flow based on the entropy generation minimization principle. The effects of wall-fluid temperature difference (ΔT) and swirl intensity (Sn) on entropy generation are considered in the pre...

The purpose of this study is to present a comparative study between Newtonian and non-Newtonian blood viscosity models for simulating the hemodynamic wall shear stress (WSS) of cerebral aneurysms. The non-Newtonian blood viscosity was modeled using the Carreau-Yasuda nonlinear model. Two realistic cerebral aneurysm models, derived from 3D angiograp...

During oil wellbore drilling processes, filter cake is formed on the sidewalls of the well hole due to filtration of drilling fluid particles. The filter cake is crucial to the drilling process, since it helps to maintain the wellbore hole, protects the drilling bit from jamming and facilitates the subsequent phases of the well development. The mos...

This article presents numerical simulations of unconfined swirl flow. The Sydney swirl flow database was used as references for the boundary conditions and experimental validation. A number of RANS turbulence models were investigated in order to explore their potential in predicting axial and swirl velocity profiles of the swirl flow field. The num...

Zanker plate is a widely used flow straightener to eliminate turbulence originating from pipe fittings in experimental fluid flow applications. In this paper, steady state, incompressible, swirling turbulent flow through Zanker plate has been studied. The solution and the analysis were carried out using finite volume CFD solver FLUENT 6.2. Five tur...

The present work presents an experimental characterization of the erosion-corrosion phenomena caused by confined slurry seawater flow. A set of experiments were conducted under a carefully controlled environment to estimate the erosion-corrosion severity in a 90° pipe bend. Sand particle concentration ranged from 0 to 9 g/l. Accurate spectrometric...

As a result of rapid urbanization in numerous cities around the world, the demand for transportation has increased rapidly, resulting in emission of high levels of exhaust pollutants into the atmosphere. This is a major cause of deterioration in the local air quality, with consequent escalating risk of adverse health conditions amongst urban inhabi...

The present work analyzes, through a rigorous numerical investigation, the entropy generation due to viscous dissipation around a Wells turbine blade. Two-dimensional numerical models for four NACA airfoils were built and validated against experimental measurements under steady flow conditions. The models were used to assess the entropy generation...

The vortex flame concept of combustion has been well known to produce low levels of NOx. This feature qualifies it to be used in industrial processes and in power generation to comply with the environmental regulations concerning nitrogen oxide emissions. An asymmetric vortex flame combustor has been recently proposed by the authors (Saqr et al., 2...

A set of numerical simulations were conducted to estimate the change in entropy generation in swirl stabilized CH4/air flames due to H2 addition to the fuel. A robust finite volume computational model solving the Reynolds Averaged Navier Stokes with a first order turbulence closure and laminar flamelet combustion model was used to compute the flow...

Numerical simulations were conducted to estimate the change in entropy generation in swirl stabilized CH4/air flame due to H2 addition to the fuel stream. A finite volume computational model which solves the Reynolds Averaged Navier Stokes with the Rε/k-ε turbulence model and laminar flamelet combustion model was used to compute the flow and energy...

In this article, we present three dimensional CFD study of turbulent vortex flow in an annular passage using OpenFOAM 1.6. The vortex flow is generated by introducing the flow through a tangential entry to the passage. For the analysis presented in this article, turbulence was modeled using the . R ε/. k-. ε model, in addition, a comparison between...

Temperature distribution is predicted through numerical simulation of a turbulent non-premixed methane flame using the standard Eddy Dissipation Model (EDM) and a model based a presumed shape of probability density function (PDF) along with an equilibrium chemistry model. Results are validated against existing experimental data. Two models are comp...

This article aims at investigating the effect of hydrogen addition on the temperature and pollutant emissions of turbulent unconfined swirling methane/air flame. A computational approach utilizing the steady laminar flamelet and the realizable k-ε combustion and turbulence models, respectively, has been used. The turbulence-combustion interaction h...

The issue of air quality conditions has become a major indicator to the quality of life in many urban areas around the world. It was affected by the air pollution in urban street canyons mainly contributed by the vehicle emitted source. Different street canyon geometry and meteorological conditions may cause pollutant accumulation inside street can...

In this paper, we present a computational investigation of the nonreacting flow structure inside a novel asymmetric vortex combustor that was recently proposed by the authors. Large Eddy Simulation using the Smagorinsky-Lilly subgrid turbulence closure has been used to study such flow. A computational grid of 2.22×106 cells was used to ensure that...

In this paper we present the result of High-Speed Reacting Flow Laboratory (HiREF) pulse detonation engine (PDE) experimental study on direct thrust measurement. The thrust force generated by the repetitive detonation from a 50 mm inner diameter and 600 mm length tube was directly measured using load cell. Shchelkin spiral was used as an accelerato...

This work presents a novel swirler with variable blade configuration for gas turbine combustors and industrial burners. The flow dynamics downstream the swirler was explored using Large Eddy Simulation (LES). The resolved turbulence kinetic energy in the region where the flow exhibits the main flow phenomena was well above 80% of the total turbulen...

In the present article we present computational and experimental investigations of a turbulent asymmetric vortex flame. Such flame was created in a novel asymmetric combustor, which is described for the first time in this article. The three dimensional isothermal and reacting flow fields have been described using a computational methodology that im...

This work discusses the implementation of eddy dissipation model in OpenFOAM CFD toolbox. The code was validated in modeling of confined non-premixed Methane jet flame. The model predictions were extensively compared against published experimental results as well as ANSYS Fluent® predictions. The differences between the implemented model in OpenFOA...

Within the eddy dissipation model of turbulent diffusion flames, the method of computing the dissipation rate of turbulence kinetic energy is vitally crucial for the accurate expression of the reaction rate. We examine the performance of four different eddy viscosity turbulence models in modeling coflowing, turbulent diffusion methane/air flame thr...

The chemical reaction rate is highly dependent on the turbulence time scale in the eddy-dissipation model of diffusion flames. In the present work, two turbulence time scales and their effect on the flame predictions are investigated. The first time scale is the large eddy time scale based on the ratio between turbulence dissipation rate and kineti...

Two turbulence models were used to comparatively predict the isothermal flow field of Sydney swirling flame. The emphasis of the present work is on the predictability of the forced vortex flow field of each turbulence model. The ε ε − k R / eddy viscosity turbulence model was used in comparison with the Launder, Reece and Rodi (LRR) Reynolds stress...

In this study, we present some theoretical notes on the use of the Boltzmann equation in computing detonation of combustible gases. The scarceness of relevant study, as well as the sensitivity of the topic, were the major motivations behind the intention to present these notes for publication. A timeline of the detonation phenomenon and its physica...

In this paper, a new variant of the k-ε turbulence model (Saqr et al., CFD Letters, 1(2) pp. 87–94) is used to compute the shear driven vortex flow in an open cylindrical cavity. The results are compared with published LDA measurements for such flow configuration. The modified turbulence model demonstrated good agreement with experimental results,...