The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Florian T. Muijres - One of the best experts on this subject based on the ideXlab platform.
-
A chordwise offset of the wing-pitch axis enhances Rotational aerodynamic Forces on insect wings: a numerical study.
Journal of the Royal Society Interface, 2019Co-Authors: Wouter G. Van Veen, Johan L. Van Leeuwen, Florian T. MuijresAbstract:Most flying animals produce aerodynamic Forces by flapping their wings back and forth with a complex wingbeat pattern. The fluid dynamics that underlies this motion has been divided into separate aerodynamic mechanisms of which Rotational lift, that results from fast wing pitch rotations, is particularly important for flight control and manoeuvrability. This Rotational Force mechanism has been modelled using Kutta-Joukowski theory, which combines the forward stroke motion of the wing with the fast pitch motion to compute Forces. Recent studies, however, suggest that hovering insects can produce Rotational Forces at stroke reversal, without a forward motion of the wing. We have conducted a broad numerical parametric study over a range of wing morphologies and wing kinematics to show that Rotational Force production depends on two mechanisms: (i) conventional Kutta-Joukowski-based Rotational Forces and (ii) a Rotational Force mechanism that enables insects with an offset of the pitch axis relative to the wing's chordwise symmetry axis to generate Rotational Forces in the absence of forward wing motion. Because flying animals produce control actions frequently near stroke reversal, this pitch-axis-offset dependent aerodynamic mechanism may be particularly important for understanding control and manoeuvrability in natural flyers.
-
Supplementary material from "A chordwise offset of the wing-pitch axis enhances Rotational aerodynamic Forces on insect wings: a numerical study"
2019Co-Authors: Wouter G. Van Veen, Johan L. Van Leeuwen, Florian T. MuijresAbstract:Most flying animals produce aerodynamic Forces by flapping their wings back and forth with a complex wingbeat pattern. The fluid dynamics that underlies this motion has been divided into separate aerodynamic mechanisms of which Rotational lift, that results from fast wing pitch rotations, is particularly important for flight control and manoeuvrability. This Rotational Force mechanism has been modelled using Kutta–Joukowski theory, which combines the forward stroke motion of the wing with the fast pitch motion to compute Forces. Recent studies, however, suggest that hovering insects can produce Rotational Forces at stroke reversal, without a forward motion of the wing. We have conducted a broad numerical parametric study over a range of wing morphologies and wing kinematics to show that Rotational Force production depends on two mechanisms: (i) conventional Kutta–Joukowski-based Rotational Forces, and (ii) a Rotational Force mechanism that enables insects with an offset of the pitch-axis relative to the wing's chordwise symmetry axis to generate Rotational Forces in the absence of forward wing motion. Because flying animals produce control actions frequently near stroke reversal, this pitch-axis-offset dependent aerodynamic mechanism may be particularly important for understanding control and manoeuvrability in natural flyers.
Joseph V. Hollweg - One of the best experts on this subject based on the ideXlab platform.
-
Deceleration of Alpha Particles in the Solar Wind by Instabilities and the Rotational Force: Implications for Heating, Azimuthal Flow, and the Parker Spiral Magnetic Field
The Astrophysical Journal, 2015Co-Authors: Daniel Verscharen, Benjamin D. G. Chandran, Sofiane Bourouaine, Joseph V. HollwegAbstract:Protons and alpha particles in the fast solar wind are only weakly collisional and exhibit a number of nonequilibrium features, including relative drifts between particle species. Two non-collisional mechanisms have been proposed for limiting differential flow between alpha particles and protons: plasma instabilities and the Rotational Force. Both mechanisms decelerate the alpha particles. In this paper, we derive an analytic expression for the rate Qflow at which energy is released by alpha-particle deceleration, accounting for azimuthal flow and conservation of total momentum. We show that instabilities control the deceleration of alpha particles at r rcrit , where r 2.5 AU crit in the fast solar wind in the ecliptic plane. We find that Qflow is positive at r rcrit < and Q 0 flow = at r rcrit , consistent with the previous finding that the Rotational Force does not lead to a release of energy. We compare the value of Qflow at r rcrit < with empirical heating rates for protons and alpha particles, denoted Qp and Qa, deduced from in situ measurements of fast-wind streams from the Helios and Ulysses spacecraft. We find that Qflow exceeds Qa at r 1A U < , and that Q Q flow p decreases with increasing distance from the Sun from a value of about one at r = 0.29–0.42 AU to about 1/4 at 1 AU. We conclude that the continuous energy input from alpha-particle deceleration at r rcrit < makes an important contribution to the heating of the fast solar wind. We also discuss the implications of the alpha-particle drift for the azimuthal flow velocities of the ions and for the Parker spiral magnetic field.
-
deceleration of alpha particles in the solar wind by instabilities and the Rotational Force implications for heating azimuthal flow and the parker spiral magnetic field
arXiv: Space Physics, 2014Co-Authors: Daniel Verscharen, Benjamin D. G. Chandran, Sofiane Bourouaine, Joseph V. HollwegAbstract:Protons and alpha particles in the fast solar wind are only weakly collisional and exhibit a number of non-equilibrium features, including relative drifts between particle species. Two non-collisional mechanisms have been proposed for limiting differential flow between alpha particles and protons: plasma instabilities and the Rotational Force. Both mechanisms decelerate the alpha particles. In this paper, we derive an analytic expression for the rate $Q_{\mathrm{flow}}$ at which energy is released by alpha-particle deceleration, accounting for azimuthal flow and conservation of total momentum. We show that instabilities control the deceleration of alpha particles at $r r_{\mathrm{crit}}$, where $r_{\mathrm{crit}} \simeq 2.5 \,\mathrm{AU}$ in the fast solar wind in the ecliptic plane. We find that $Q_{\mathrm{flow}}$ is positive at $r
Wouter G. Van Veen - One of the best experts on this subject based on the ideXlab platform.
-
A chordwise offset of the wing-pitch axis enhances Rotational aerodynamic Forces on insect wings: a numerical study.
Journal of the Royal Society Interface, 2019Co-Authors: Wouter G. Van Veen, Johan L. Van Leeuwen, Florian T. MuijresAbstract:Most flying animals produce aerodynamic Forces by flapping their wings back and forth with a complex wingbeat pattern. The fluid dynamics that underlies this motion has been divided into separate aerodynamic mechanisms of which Rotational lift, that results from fast wing pitch rotations, is particularly important for flight control and manoeuvrability. This Rotational Force mechanism has been modelled using Kutta-Joukowski theory, which combines the forward stroke motion of the wing with the fast pitch motion to compute Forces. Recent studies, however, suggest that hovering insects can produce Rotational Forces at stroke reversal, without a forward motion of the wing. We have conducted a broad numerical parametric study over a range of wing morphologies and wing kinematics to show that Rotational Force production depends on two mechanisms: (i) conventional Kutta-Joukowski-based Rotational Forces and (ii) a Rotational Force mechanism that enables insects with an offset of the pitch axis relative to the wing's chordwise symmetry axis to generate Rotational Forces in the absence of forward wing motion. Because flying animals produce control actions frequently near stroke reversal, this pitch-axis-offset dependent aerodynamic mechanism may be particularly important for understanding control and manoeuvrability in natural flyers.
-
Supplementary material from "A chordwise offset of the wing-pitch axis enhances Rotational aerodynamic Forces on insect wings: a numerical study"
2019Co-Authors: Wouter G. Van Veen, Johan L. Van Leeuwen, Florian T. MuijresAbstract:Most flying animals produce aerodynamic Forces by flapping their wings back and forth with a complex wingbeat pattern. The fluid dynamics that underlies this motion has been divided into separate aerodynamic mechanisms of which Rotational lift, that results from fast wing pitch rotations, is particularly important for flight control and manoeuvrability. This Rotational Force mechanism has been modelled using Kutta–Joukowski theory, which combines the forward stroke motion of the wing with the fast pitch motion to compute Forces. Recent studies, however, suggest that hovering insects can produce Rotational Forces at stroke reversal, without a forward motion of the wing. We have conducted a broad numerical parametric study over a range of wing morphologies and wing kinematics to show that Rotational Force production depends on two mechanisms: (i) conventional Kutta–Joukowski-based Rotational Forces, and (ii) a Rotational Force mechanism that enables insects with an offset of the pitch-axis relative to the wing's chordwise symmetry axis to generate Rotational Forces in the absence of forward wing motion. Because flying animals produce control actions frequently near stroke reversal, this pitch-axis-offset dependent aerodynamic mechanism may be particularly important for understanding control and manoeuvrability in natural flyers.
Maria Drangova - One of the best experts on this subject based on the ideXlab platform.
-
Hip capsular strain varies between ligaments dependent on both hip position- and applied Rotational Force
Knee Surgery Sports Traumatology Arthroscopy, 2020Co-Authors: Timothy A. Burkhart, Pardis Baha, Alexandra Blokker, Ivailo Petrov, David W. Holdsworth, Maria Drangova, Alan Getgood, Ryan M. DegenAbstract:Purpose To noninvasively characterize the ligament strain in the hip capsule using a novel CT-based imaging technique. Methods The superior iliofemoral ligament (SIFL), inferior iliofemoral ligament (IIFL), ischiofemoral ligament (IFL) and pubofemoral ligament (PFL) were identified and beaded in seven cadavers. Specimens were mounted on a joint motion simulator within an O-arm CT scanner in − 15°, 0°, 30°, 60°, and 90° of flexion. 3 Nm of internal rotation (IR) and external rotation (ER) were applied and CT scans obtained. Strains were calculated by comparing bead separation in loaded and unloaded conditions. Repeated-measures ANOVA was used to evaluate differences in strain within ligaments between hip positions. Results For the SIFL, strain significantly decreased in IR at 30° ( p = 0.045) and 60° ( p = 0.043) versus 0°. For ER, there were no significant position-specific changes in strain (n.s.). For the IIFL, strain decreased in IR and increased in ER with no significant position-specific differences. For the IFL, strain increased with IR and decreased with ER with no significant position-specific differences. Finally, in the PFL there was a significant flexion angle-by-load interaction ( p
-
Hip capsular strain varies between ligaments dependent on both hip position- and applied Rotational Force.
Knee surgery sports traumatology arthroscopy : official journal of the ESSKA, 2020Co-Authors: Timothy A. Burkhart, Pardis Baha, Alexandra Blokker, Ivailo Petrov, David W. Holdsworth, Maria Drangova, Alan Getgood, Ryan M. DegenAbstract:To noninvasively characterize the ligament strain in the hip capsule using a novel CT-based imaging technique. The superior iliofemoral ligament (SIFL), inferior iliofemoral ligament (IIFL), ischiofemoral ligament (IFL) and pubofemoral ligament (PFL) were identified and beaded in seven cadavers. Specimens were mounted on a joint motion simulator within an O-arm CT scanner in − 15°, 0°, 30°, 60°, and 90° of flexion. 3 Nm of internal rotation (IR) and external rotation (ER) were applied and CT scans obtained. Strains were calculated by comparing bead separation in loaded and unloaded conditions. Repeated-measures ANOVA was used to evaluate differences in strain within ligaments between hip positions. For the SIFL, strain significantly decreased in IR at 30° (p = 0.045) and 60° (p = 0.043) versus 0°. For ER, there were no significant position-specific changes in strain (n.s.). For the IIFL, strain decreased in IR and increased in ER with no significant position-specific differences. For the IFL, strain increased with IR and decreased with ER with no significant position-specific differences. Finally, in the PFL there was a significant flexion angle-by-load interaction (p
-
hip capsular strain varies between ligaments dependent on both hip position and applied Rotational Force
Knee Surgery Sports Traumatology Arthroscopy, 2020Co-Authors: Timothy A. Burkhart, Pardis Baha, Alexandra Blokker, Ivailo Petrov, David W. Holdsworth, Maria DrangovaAbstract:To noninvasively characterize the ligament strain in the hip capsule using a novel CT-based imaging technique. The superior iliofemoral ligament (SIFL), inferior iliofemoral ligament (IIFL), ischiofemoral ligament (IFL) and pubofemoral ligament (PFL) were identified and beaded in seven cadavers. Specimens were mounted on a joint motion simulator within an O-arm CT scanner in − 15°, 0°, 30°, 60°, and 90° of flexion. 3 Nm of internal rotation (IR) and external rotation (ER) were applied and CT scans obtained. Strains were calculated by comparing bead separation in loaded and unloaded conditions. Repeated-measures ANOVA was used to evaluate differences in strain within ligaments between hip positions. For the SIFL, strain significantly decreased in IR at 30° (p = 0.045) and 60° (p = 0.043) versus 0°. For ER, there were no significant position-specific changes in strain (n.s.). For the IIFL, strain decreased in IR and increased in ER with no significant position-specific differences. For the IFL, strain increased with IR and decreased with ER with no significant position-specific differences. Finally, in the PFL there was a significant flexion angle-by-load interaction (p < 0.001; ES = 0.566), with peak strains noted at 60˚, however pair-wise comparisons failed to identify significant differences between positions (n.s.). Strain decreased in ER, with no significant position-specific differences. The SIFL and IIFL limit hip external rotation with greater effect in higher flexion angles, while the IFL and PFL limit hip internal rotation. Following hip arthroscopy, consideration should be given to restricting external rotation as traditional capsulotomies cause injury to the SIFL and IIFL.
Johan L. Van Leeuwen - One of the best experts on this subject based on the ideXlab platform.
-
A chordwise offset of the wing-pitch axis enhances Rotational aerodynamic Forces on insect wings: a numerical study.
Journal of the Royal Society Interface, 2019Co-Authors: Wouter G. Van Veen, Johan L. Van Leeuwen, Florian T. MuijresAbstract:Most flying animals produce aerodynamic Forces by flapping their wings back and forth with a complex wingbeat pattern. The fluid dynamics that underlies this motion has been divided into separate aerodynamic mechanisms of which Rotational lift, that results from fast wing pitch rotations, is particularly important for flight control and manoeuvrability. This Rotational Force mechanism has been modelled using Kutta-Joukowski theory, which combines the forward stroke motion of the wing with the fast pitch motion to compute Forces. Recent studies, however, suggest that hovering insects can produce Rotational Forces at stroke reversal, without a forward motion of the wing. We have conducted a broad numerical parametric study over a range of wing morphologies and wing kinematics to show that Rotational Force production depends on two mechanisms: (i) conventional Kutta-Joukowski-based Rotational Forces and (ii) a Rotational Force mechanism that enables insects with an offset of the pitch axis relative to the wing's chordwise symmetry axis to generate Rotational Forces in the absence of forward wing motion. Because flying animals produce control actions frequently near stroke reversal, this pitch-axis-offset dependent aerodynamic mechanism may be particularly important for understanding control and manoeuvrability in natural flyers.
-
Supplementary material from "A chordwise offset of the wing-pitch axis enhances Rotational aerodynamic Forces on insect wings: a numerical study"
2019Co-Authors: Wouter G. Van Veen, Johan L. Van Leeuwen, Florian T. MuijresAbstract:Most flying animals produce aerodynamic Forces by flapping their wings back and forth with a complex wingbeat pattern. The fluid dynamics that underlies this motion has been divided into separate aerodynamic mechanisms of which Rotational lift, that results from fast wing pitch rotations, is particularly important for flight control and manoeuvrability. This Rotational Force mechanism has been modelled using Kutta–Joukowski theory, which combines the forward stroke motion of the wing with the fast pitch motion to compute Forces. Recent studies, however, suggest that hovering insects can produce Rotational Forces at stroke reversal, without a forward motion of the wing. We have conducted a broad numerical parametric study over a range of wing morphologies and wing kinematics to show that Rotational Force production depends on two mechanisms: (i) conventional Kutta–Joukowski-based Rotational Forces, and (ii) a Rotational Force mechanism that enables insects with an offset of the pitch-axis relative to the wing's chordwise symmetry axis to generate Rotational Forces in the absence of forward wing motion. Because flying animals produce control actions frequently near stroke reversal, this pitch-axis-offset dependent aerodynamic mechanism may be particularly important for understanding control and manoeuvrability in natural flyers.
