# Manuel García-Villalba's research while affiliated with TU Wien and other places

**What is this page?**

This page lists the scientific contributions of an author, who either does not have a ResearchGate profile, or has not yet added these contributions to their profile.

It was automatically created by ResearchGate to create a record of this author's body of work. We create such pages to advance our goal of creating and maintaining the most comprehensive scientific repository possible. In doing so, we process publicly available (personal) data relating to the author as a member of the scientific community.

If you're a ResearchGate member, you can follow this page to keep up with this author's work.

If you are this author, and you don't want us to display this page anymore, please let us know.

It was automatically created by ResearchGate to create a record of this author's body of work. We create such pages to advance our goal of creating and maintaining the most comprehensive scientific repository possible. In doing so, we process publicly available (personal) data relating to the author as a member of the scientific community.

If you're a ResearchGate member, you can follow this page to keep up with this author's work.

If you are this author, and you don't want us to display this page anymore, please let us know.

## Publications (86)

Clot formation is a crucial process that prevents bleeding, but can lead to severe disorders when imbalanced. This process is regulated by the coagulation cascade, a biochemical network that controls the enzyme thrombin, which converts soluble fibrinogen into the fibrin fibers that constitute clots. Coagulation cascade models are typically complex...

Background: In the setting of ST-segment elevation myocardial infarction (STEMI), imaging-based biomarkers could be useful for guiding oral anticoagulation for primary prevention of stroke.
Objectives: To test the efficacy of intraventricular blood stasis imaging for predicting a composite primary endpoint of cardioembolic risk during the first 6 m...

Clot formation is a crucial process that prevents bleeding, but can lead to severe disorders when imbalanced. This process is regulated by the coagulation cascade, a biochemical network that controls the enzyme thrombin, which converts soluble fibrinogen into the fibrin fibers that constitute clots. Coagulation cascade models are typically complex...

Disruptions to left atrial (LA) blood flow, such as those caused by atrial fibrillation (AF), can lead to thrombosis in the left atrial appendage (LAA) and an increased risk of systemic embolism. LA hemodynamics are influenced by various factors, including LA anatomy and function, and pulmonary vein (PV) inflow conditions. In particular, the PV flo...

We present a simple modification of the direct-forcing immersed boundary method (IBM) proposed by Uhlmann [J. Comput. Phys, 2005] in order to enable it to be applied to particulate flows with solid-to-fluid density ratios around unity. The main difference with respect to the original formulation lies in the particle velocity update which is perform...

We have performed particle-resolved direct numerical simulations of many heavy non-spherical particles settling under gravity in the dilute regime. The particles are oblate spheroids of aspect ratio $1.5$ and density ratio $1.5$ . Two Galileo numbers are considered, namely $111$ and $152$ , for which a single oblate spheroid follows a steady vertic...

Disruptions to left atrial (LA) blood flow, such as those caused by atrial fibrillation (AF), can lead to thrombosis in the left atrial appendage (LAA) and an increased risk of systemic embolism. LA hemodynamics are influenced by various factors, including LA anatomy and function, and pulmonary vein (PV) inflow conditions. In particular, the PV flo...

We have performed particle-resolved direct numerical simulations of many heavy non-spherical particles settling under gravity in the dilute regime. The particles are oblate spheroids of aspect ratio 1.5 and density ratio 1.5. Two Galileo numbers are considered, namely 111 and 152, for which a single oblate spheroid follows a steady vertical and a s...

We present a method for computing fluid–structure interaction problems for multi-body systems. The fluid flow equations are solved using a fractional-step method with the immersed boundary method proposed by Uhlmann (2005). The equations of the rigid bodies are solved using recursive algorithms proposed by Felis (2017). The two systems of equations...

The lack of mechanically effective contraction of the left atrium (LA) during atrial fibrillation (AF) disturbs blood flow, increasing the risk of thrombosis and ischemic stroke. Thrombosis is most likely in the left atrial appendage (LAA), a small narrow sac where blood is prone to stagnate. Slow flow promotes the formation of erythrocyte aggregat...

Tandem configurations of two self-propelled flexible flappers of finite span are explored by means of numerical simulations. The same sinusoidal vertical motion is imposed on the leading edge of both flappers, but with a phase shift (φ). In addition, a vertical offset, H, is prescribed between the flappers. The configurations that emerge are charac...

We report direct numerical simulations of a pair of wings in horizontal tandem configuration to analyze the effect of their aspect ratio on the flow and the aerodynamic performance of the system. The wings are immersed in a uniform free stream at the Reynolds number Re = 1000, and they undergo heaving and pitching oscillation with the Strouhal numb...

We report direct numerical simulations of a pair of wings in horizontal tandem configuration, to analyze the effect of their aspect ratio on the flow and the aerodynamic performance of the system. The wings are immersed in a uniform free-stream at Reynolds number Re = 1000, and they undergo heaving and pitching oscillation with Strouhal number St =...

We present a method for computing fluid-structure interaction problems for multi-body systems. The fluid flow equations are solved using a fractional-step method with the immersed boundary method proposed by Uhlmann [J. Comput Phys. 209 (2005) 448]. The equations of the rigid bodies are solved using recursive algorithms proposed by Felis [Auton. Ro...

Atrial fibrillation (AF) is the most common arrhythmia, affecting ~35M people worldwide. The irregular beating of the left atrial (LA) caused by AF impacts the LA hemodynamics increasing the risk of thrombosis and ischemic stroke. Most LA thrombi appear in its appendage (LAA), a narrow sac of varied morphology where blood is prone to stagnate. In t...

Atrial fibrillation (AF) alters left atrial (LA) hemodynamics, which can lead to thrombosis in the left atrial appendage (LAA), systemic embolism and stroke. A personalized risk-stratification of AF patients for stroke would permit improved balancing of preventive anticoagulation therapies against bleeding risk. We investigated how LA anatomy and f...

We present two-dimensional and three-dimensional (3-D) direct numerical simulations of large-amplitude plunging maneuvers at Reynolds numbers of Re=1000 and 5000, with velocity ratios of G=0.5, 1, and 2. For all cases, the evolution of the force coefficients is qualitatively similar. The lift coefficient presents a pronounced peak toward the end of...

We present experiments and simulations of plunging maneuvers of large amplitude, for velocity ratios of G=1 and 2, defined as the ratio between the peak plunge velocity and the freestream velocity. We explore the effect of the airfoil shape by considering a NACA 0012 wing and a flat plate. The experiments are performed with wings with aspect ratios...

In the present article, we report results of Direct Numerical Simulations (DNS) of a pressure-driven fully developed turbulent flow in a pipe, with sinusoidal heat flux boundary conditions, and with temperature-dependent viscosity and thermal diffusivity, representative of the conditions in the tubes of heat receivers in Solar Power Tower plants.

Contrary to birds, bats and most insects, dragonflies have two pairs of wings arranged in a tandem configuration which can move independently (Norberg in Swimming and Flying in Nature, pp. 763-781, 1975 [1]; Thomas et al. J Exp Biol 207(24):4299-4323, 2004 [2]). By modifying the kinematics and the phase relationship between the fore and hind pair o...

Over the past two decades, cardiologists and engineers have increasingly worked together to describe and understand the blood flow in the left ventricle (LV).

Atrial fibrillation (AF) alters left atrial (LA) hemodynamics, which can lead to thrombosis in the left atrial appendage (LAA), systemic embolism and stroke. A personalized risk-stratification of AF patients for stroke would permit improved balancing of preventive anticoagulation therapies against bleeding risk. We investigated how LA anatomy and f...

Direct numerical simulations have been performed to analyze how three-dimensional effects influence the performance of wings in tandem configuration undergoing a two-dimensional optimal kinematics. This optimal motion is a combination of heaving and pitching of the airfoils in a uniform free-stream at a Reynolds number Re=1000 and Strouhal number S...

This paper reports a combined experimental and numerical study of the flow over a rigid airfoil in flapping motion. The setup consists of a heaving and pitching airfoil at a moderate Reynolds number ([Formula: see text]), at a Strouhal number St = 0.1. The aim is to assess the accuracy of two-dimensional direct numerical simulations in predicting a...

Unsteady aerodynamics at low Reynolds number is receiving an increasing attention from the scientific community due to the recent development of Flapping Micro Air Vehicles (FMAV). These vehicles generate thrust and lift by flapping their wings, like insects or small birds do. The specific unsteady aerodynamic mechanisms involved in the generation...

As samara seeds fall from trees, they enter into auto-rotation. In this way they maximize dispersal distances (Green, Am J Bot 169:1218–1224, 1998, [2]). In this study, we present direct numerical simulations of the autorotation of a model samara at Reynolds numbers, Re, somewhat smaller than those observed in nature. The aim is to detect the prese...

Direct Numerical Simulations of the flow around a pair of flapping wings are presented. The wings are flying in forward flight at a Reynolds number Re=500, flapping at a reduced frequency k=1. Several values of the radius of flapping motion are considered, resulting in a database that shows a smooth transition from the wing rotating with respect to...

This study presents a computational tool to accurately simulate the flow around a flapping-wing micro air vehicle in free flight. The flow around the vehicle is obtained by solving the Navier–Stokes equations of the incompressible flow using an immersed boundary method. The motion of the vehicle subject to aerodynamic and gravity forces is obtained...

In this study the flow around a winged-seed in auto-rotation is characterized using direct numerical simulations (DNS) at Reynolds number in the range 80–240, based on the descent speed and a characteristic chord length. In this range, the flow is approximately steady when observed from a reference frame fixed to the seed. For all cases, the flow s...

This manuscript analyzes the role of coherent structures in turbulent thermal transport in pipe flows. A Proper Orthogonal Decomposition (POD) analysis is performed on a direct numerical simulation dataset with non-homogeneous boundary conditions, heated on the upper side, representative of solar receivers (Antoranz et al., 2015, Int. J. Heat Fluid...

In this study, we report large eddy simulations of turbulent flow in a periodic compound meandering channel for three different depth conditions: one in-bank and two overbank conditions. The flow configuration corresponds to the experiments of Shiono and Muto (1998). The predicted mean streamwise velocities, mean secondary motions, velocity fluctua...

Numerical simulations of the auto-rotation of a model winged seed are presented. The calculations are performed by solving simultaneously the Navier-Stokes equations for the flow surrounding the seed and the rigid-body equations for the motion of the seed. The Reynolds number based on the descent speed and a characteristic chord length is varied in...

Kite Flight Simulators Based on Minimal Coordinate Formulations

Direct numerical simulations of a temporally-developing, low-speed, variable-density, turbulent, plane mixing layer are performed. The Navier-Stokes equations in the low-Mach number approximation are solved using a novel algorithm based on an extended version of the velocity-vorticity formulation used by Kim et al. (1987) for incompressible flows....

This paper presents large eddy simulation of turbulent flow in a meandering open channel with smooth wall and rectangular cross-section. The Reynolds number based on the channel height is 40,000 and the aspect ratio of the cross-section is 4.48. The depth-averaged mean stream-wise velocity agree well to experimental measurements. In this specific c...

The influence that the kinematics of pitching and heaving 2D airfoils have on the aerodynamic forces is investigated using Direct Numerical Simulations and a force decomposition algorithm. Large amplitude motions are considered (of the order of one chord), with moderate Reynolds numbers and reduced frequencies of order 1, varying the mean pitch ang...

A mathematical model of a kite connected to the ground by two straight tethers of varying lengths is presented and used to study the traction force generated by kites flying in cross-wind conditions. The equations of motion are obtained by using a Lagrangian formulation, which yields a low-order system of ordinary differential equations free of con...

We present a stability analysis of a plunging and pitching wing of infinite aspect ratio at low Reynolds number. Four cases are considered by varying the mean pitch angle and the phase shift between pitching and plunging. Each case is studied by performing two dimensional DNS and Floquet stability analysis. The four cases considered display differe...

This paper presents a thermal analysis of thin-wall pipes under non-uniform heat flux in the circumferential direction, with a turbulent flow in statistically stationary state inside. The temperature distribution in the solid and in the fluid is obtained using an spectral method that solves the conjugate heat transfer problem. Special attention is...

We present some preliminary results of direct numerical simulations of three-dimensional, temporal, plane mixing layers with variable density. The simulations are run with a parallel in-house code that solves the Navier-Stokes equations in the Low-Mach number approximation, using a novel algorithm based on an extended version of the velocity-vortic...

We present some preliminary results of direct numerical simulations of three-dimensional, temporal, plane mixing layers with variable density. The simulations are run with a parallel in-house code that solves the Navier-Stokes equations in the Low-Mach number approximation, using a novel algorithm based on an extended version of the velocity-vortic...

Direct numerical simulations of heat transfer in a fully-developed turbulent pipe flow with circumferentially-varying thermal boundary conditions are reported. Three cases have been considered for friction Reynolds number in the range 180–360 and Prandtl number in the range 0.7–4. The temperature statistics under these heating conditions are charac...

We present fully resolved Direct Numerical Simulations of 2D flow over a moving airfoil, using an in-house code that solves the Navier-Stokes equations of the incompressible flow with an Immersed Boundary Method. A combination of sinusoidal plunging and pitching motions is imposed to the airfoil. Starting from a thrust producing case (Reynolds numb...

The tubes of central receiver power plants are designed to work under very demanding conditions, with heat fluxes varying between 0.2 to 1 MW/m2, depending on both the weather conditions and the operating regime of the plant. Also, the heat flux is localized along the circumferential coordinate of the tube, on the outward facing side of the tube. T...

We present preliminary results of direct numerical simulations of a turbulent mixing layer with variable density. These simulations are a first step in the development of a numerical solver able to simulate spray diffusion flames in the limit of infinitely fast chemical reaction, using the coupling-function formulation1. The set-up of the simulatio...

This paper presents a large eddy simulation of forced convection heat transfer in the flow around a surface-mounted finite-height circular cylinder. The study was carried out for a cylinder with height-to-diameter ratio of 2.5, a Reynolds number based on the cylinder diameter of 44 000 and a Prandtl number of 1. Only the surface of the cylinder is...

In this paper we provide a description of the three-dimensional flow induced by a sequence of lateral obstacles in a straight shallow open-channel flow with flat bathymetry. The obstacles are modelled as rectangular blocks and are located at one channel wall, perpendicular to the main stream direction. Two aspect ratios of the resulting dead zones...

Data from direct numerical simulation of open channel flow over a
geometrically rough wall at a bulk Reynolds number of 2900, generated by
Chan-Braun et al. ["Force and torque acting on particles in a transitionally
rough open-channel flow", J. Fluid Mech. 684, 441--474 (2011),
10.1017/jfm.2011.311] are further analysed with respect to the time and...

We have performed a direct numerical simulation of dilute turbulent
particulate flow in a vertical plane channel, fully resolving the phase
interfaces. The flow conditions are the same as those in the main case of
"Uhlmann, M., Phys. Fluids, vol. 20, 2008, 053305", with the exception of the
computational domain length which has been doubled in the...

This paper presents a large eddy simulation of mass transfer in the flow around a surface-mounted finite-height circular cylinder.
The study was carried out for a cylinder with height-to-diameter ratio of 2.5 and a Reynolds number based on the cylinder
diameter of 44000. The approach flow boundary layer had a thickness of about 10% of the cylinder...

We studied stably-stratified, fully-developed, turbulent channel flow
using linear stability analysis. The analysis considered the mean
velocity and density profiles extracted from DNS [1] calculations as
base flow, and included a linear model to represent the energy
dissipation and scalar diffusion felt at the large scales as a
consequence of the...

The identification of the spatial characteristics and the shedding frequencies of coherent structures in shallow flows usually involves the use of sophisticated equipment for velocity measurements such as laser Doppler anemometry or particle image velocimetry. In this work, a simple and low-cost alternative for the quantitative characterization of...

Direct numerical simulation of open channel flow over a geometrically rough
wall has been performed at a bulk Reynolds number of approximately 2900. The
wall consisted of a layer of spheres in a square arrangement. Two cases have
been considered. In the first case the spheres are small (with diameter
equivalent to 10.7 wall units) and the limit of...

Direct numerical simulations of stably stratified, turbulent channel flow at low to moderate Reynolds number have been performed using large computational boxes and considering a wide range of stratification levels. For weak stratification or high Reynolds number, the turbulence is affected by buoyancy in the core of the channel, but the near-wall...

Direct numerical simulations of interface-resolved sediment transport in horizontal open-channel flow are currently being
performed on the XC-4000. The channel bottom boundary is roughened with a fixed layer of spheres and about 9000 particles
are allowed to move within the computational domain. The density ratio of the solid and fluid phase is 1.7...

Direct numerical simulations (DNS) of stably-stratified, turbulent plane Couette flow are currently being performed on the XC-4000. The friction Reynolds number is kept approximately constant, Re
τ
≃540 and the Richardson number Ri
w
varies between 0 and 0.1. The flow is divided into two regions: the region close to the wall and the core region. Th...

Large-eddy simulations of a flow at a moderate Reynolds number over and around a three-dimensional hill have been performed. The main aim of the simulations was to study the effects of various inflow conditions (boundary layer thickness and laminar versus turbulent boundary layers) on the flow behind the hill. The main features of the flow behind t...

The hydrodynamic interaction of a fluid with a rough wall results in a net force on the roughness elements. This can cause erosion of the roughness elements – an important aspect for sediment transport in rivers or the transport of solid media by fluids in mechanical applications. In order to deepen the understanding of the processes that lead to e...

The paper examines, by means of highly resolved large-eddy simulations, the fluid mechanic behaviour of an incompressible, turbulent flow separating from an axisymmetric, hill-shaped obstacle. The hill is subjected to a turbulent flat-plate boundary layer of thickness half of the hill height, developing within a large duct in which the hill is plac...

We compute the optimal transient growth of perturbations sustained by a turbulent channel flow following the same approach recently used by del Álamo and Jiménez [J. Fluid Mech. 559, 205 (2006)]. Contrary to this previous analysis, we use generalized Orr-Sommerfeld and Squire operators consistent with previous investigations of mean flows with vari...

Direct numerical simulations (DNS) of stably-stratified, turbulent channel flow at moderate Reynolds number are currently
being performed on the XC-4000. A wide range of stratification levels is being considered and large computational boxes are
being employed to study carefully the effects of stratification on the wall turbulence. First and second...

The paper presents large eddy simulations of co-annular swirling jets into an open domain. In each of the annuli a passive
scalar is introduced and its transport is computed. If the exit of the pilot jet is retracted strong coherent flow structures
are generated which substantially impact on the transport and mixing of the scalars. Average and inst...

A highly-resolved Large Eddy Simulation of high Reynolds number flow over and around a three-dimensional hill is currently
being performed on the NEC SX-8. The principal aim of the study is to generate target results against which Hybrid LES-RANS
methods can be validated. The complex flow separation in the lee of the hill is illustrated by displayi...

This paper presents a large eddy simulation LES of turbulent open channel flow over two-dimensional periodic dunes. The Reynolds number R based on the bulk velocity Ubulk and the maximum flow depth h, is approximately 25,000. The instantaneous flow field is investigated with special emphasis on the occurrence of coherent structures. Instantaneous v...

A series of Large Eddy Simulations (LES) of non-reacting flow in a swirl burner has been performed. The configuration consists
of two unconfined co-annular jets at a Reynolds number of 81500. The flow is characterized by a Swirl number of 0.93. Two
cases are studied differing with respect to the axial location of the inner pilot jet. It was observe...

The paper presents large eddy simulation of unconfined swirling jets. In the first part, an unconfined annular jet is investigated for swirl numbers ranging from 0 to 1.2. The impact of the swirl on the mean flow and the precessing vortex structures in this flow is analysed. In the second part of the paper, a co-annular pilot jet is introduced near...

Large eddy simulations of co-annular swirling jets are performed. Two cases are considered differing with respect to the axial location of the inner jet. Mean velocities and turbulent fluctuations are in good agreement with experimental data. With the inner jet retracted, flow oscillations are considerably stronger and their computed frequency is i...

In this paper; the non-reacting flow in a swirl burner is studied using Large Eddy Simulation. The configuration consists of two unconfined co-annular jets at a Reynolds number of 81500. The flow is characterized by a Swirl number of 0.93. Two cases are studied in the paper differing with respect to the axial location of the inner pilot jet. It was...

The paper presents large eddy simulation of unconfined swirling jets. In the first part, an unconfined annular jet is investigated for swirl numbers ranging from 0 to 1.2. The impact of the swirl on the mean flow and the precessing vortex structures in this flow is analysed. In the second part of the paper, a co-annular pilot jet is introduced near...

Large eddy simulations of swirling flow in a coaxial-jet combustor are reported. Two experimental test cases have been chosen from the literature. In both cases the configuration consists of two coaxial jets which enter into an expansion duct with the annular jet being swirled, the inner jet unswirled. The main features of the flow are well predict...