scholarly journals In vivo recording of aerodynamic force with an aerodynamic force platform: from drones to birds

2015 ◽  
Vol 12 (104) ◽  
pp. 20141283 ◽  
Author(s):  
David Lentink ◽  
Andreas F. Haselsteiner ◽  
Rivers Ingersoll
Keyword(s):  
Force Measurement ◽  
Aerodynamic Force ◽  
Force Platform ◽  
Control Surface ◽  
Flapping Wings ◽  
Free Flight ◽  
Navier Stokes Equation ◽  
Flow Measurements ◽  
Weight Support

Flapping wings enable flying animals and biomimetic robots to generate elevated aerodynamic forces. Measurements that demonstrate this capability are based on experiments with tethered robots and animals, and indirect force calculations based on measured kinematics or airflow during free flight. Remarkably, there exists no method to measure these forces directly during free flight. Such in vivo recordings in freely behaving animals are essential to better understand the precise aerodynamic function of their flapping wings, in particular during the downstroke versus upstroke. Here, we demonstrate a new aerodynamic force platform (AFP) for non-intrusive aerodynamic force measurement in freely flying animals and robots. The platform encloses the animal or object that generates fluid force with a physical control surface, which mechanically integrates the net aerodynamic force that is transferred to the earth. Using a straightforward analytical solution of the Navier–Stokes equation, we verified that the method is accurate. We subsequently validated the method with a quadcopter that is suspended in the AFP and generates unsteady thrust profiles. These independent measurements confirm that the AFP is indeed accurate. We demonstrate the effectiveness of the AFP by studying aerodynamic weight support of a freely flying bird in vivo . These measurements confirm earlier findings based on kinematics and flow measurements, which suggest that the avian downstroke, not the upstroke, is primarily responsible for body weight support during take-off and landing.

scholarly journals How oscillating aerodynamic forces explain the timbre of the hummingbird’s hum and other animals in flapping flight

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Ben J Hightower ◽  
Patrick W A Wijnings ◽  
Rick Scholte ◽  
Rivers Ingersoll ◽  
Diana D Chin ◽  
...  
Keyword(s):  
Aerodynamic Force ◽  
Microphone Array ◽  
Flapping Wings ◽  
Acoustic Model ◽  
Acoustic Measurements ◽  
Aerodynamic Forces ◽  
Drag Forces ◽  
Radiated Power ◽  
Lift And Drag

How hummingbirds hum is not fully understood, but its biophysical origin is encoded in the acoustic nearfield. Hence, we studied six freely hovering Anna's hummingbirds, performing acoustic nearfield holography using a 2176 microphone array in vivo, while also directly measuring the 3D aerodynamic forces using a new aerodynamic force platform. We corroborate the acoustic measurements by developing an idealized acoustic model that integrates the aerodynamic forces with wing kinematics, which shows how the timbre of the hummingbird's hum arises from the oscillating lift and drag forces on each wing. Comparing birds and insects, we find that the characteristic humming timbre and radiated power of their flapping wings originates from the higher harmonics in the aerodynamic forces that support their bodyweight. Our model analysis across insects and birds shows that allometric deviation makes larger birds quieter and elongated flies louder, while also clarifying complex bioacoustic behavior.

scholarly journals Fluid moment and force measurement based on control surface integration

2019 ◽  
Vol 61 (1) ◽  
Author(s):  
Diana D. Chin ◽  
David Lentink
Keyword(s):  
Particle Image ◽  
Force Measurement ◽  
Aerodynamic Force ◽  
Center Of Mass ◽  
Measurement Techniques ◽  
Control Surface ◽  
Fluid Forces ◽  
Surface Integration ◽  
Image Velocimetry ◽  
Unconstrained Motion

Abstract The moments and torques acting on a deforming body determine its stability and maneuverability. For animals, robots, vehicles, and other deforming objects locomoting in liquid or gaseous fluids, these fluid moments are challenging to accurately measure during unconstrained motion. Particle image velocimetry and aerodynamic force platforms have the potential to resolve this challenge through the use of control surface integration. These measurement techniques have previously been used to recover fluid forces. Here, we show how control surface integration can similarly be used to recover the 3D fluid moments generated about a deforming body’s center of mass. We first derive a general formulation that can be applied to any body locomoting in a fluid. We then show when and how this formulation can be greatly simplified without loss of accuracy for conditions commonly encountered during fluid experiments, such as for tests done in wind or water channels. Finally, we provide detailed formulations to show how measurements from an aerodynamic force platform can be used to determine the net instantaneous moments generated by a freely flying body. These formulations also apply more generally to other fluid applications, such as underwater swimming or locomotion over water surfaces. Graphic abstract

Time-Accurate Simulation of Longitudinal Flight Mechanics with Control by CFD/RBD Coupling

2012 ◽  
Vol 226-228 ◽  
pp. 788-792 ◽  
Author(s):  
Dong Guo ◽  
Min Xu ◽  
Shi Lu Chen
Keyword(s):  
Computational Study ◽  
Rigid Motion ◽  
Rigid Body Dynamics ◽  
Flight Mechanics ◽  
Control Surface ◽  
Free Flight ◽  
Body Dynamics ◽  
Computational Fluid Dynamics Cfd ◽  
Coupled Solution ◽  
Surface Deflections

This paper describes a multidisciplinary computational study undertaken to compute the flight trajectories and simultaneously predict the unsteady free flight aerodynamics of aircraft in time domain using an advanced coupled computational fluid dynamics (CFD)/rigid body dynamics (RBD) technique. This incorporation of the flight mechanics equations and controller into the CFD solver loop and the treatment of the mesh, which must move with both the control surface deflections and the rigid motion of the aircraft, are illustrated. This work is a contribution to a wider effort towards the simulation of aeroelastic and flight stability in regions where nonlinear aerodynamics, and hence potentially CFD, can play a key role. Results demonstrating the coupled solution are presented.

scholarly journals Aerodynamic characteristics of a free-flight scramjet vehicle in shock tunnel

2021 ◽  
Vol 62 (7) ◽  
Author(s):  
Marie Tanno ◽  
Hideyuki Tanno
Keyword(s):  
System Analysis ◽  
Force Measurement ◽  
Prediction Interval ◽  
Angular Acceleration ◽  
Aerodynamic Characteristics ◽  
Measurement Precision ◽  
Shock Tunnel ◽  
Free Flight ◽  
Vehicle Model ◽  
Aerodynamic Test

Abstract A multi-component aerodynamic test for an airframe-engine integrated scramjet vehicle model was conducted in the free-piston shock tunnel HIEST. A free-flight force measurement technique was applied to the scramjet vehicle model named MoDKI. A new method using multiple piezoelectric accelerometers was developed based on overdetermined system analysis. Its unique features are the following: (1) The accelerometer’s mounting location can be more flexible. (2) The measurement precision is predicted to be improved by increasing the number of accelerometers. (3) The angular acceleration can be obtained with single-axis translational accelerometers instead of gyroscopes. (4) Through the averaging process of the multiple accelerometers, model natural vibration is expected to be mitigated. With eight model-onboard single-axis accelerometers, the three-component aerodynamic coefficients (Drag, Lift, and Pitching moment) of MoDKI were successfully measured at the angle of attack from 0.7 to 3.4 degrees under a Mach 8 free-stream test flow condition. A linear regression fitting revealed a 95% prediction interval as the measurement precision of each aerodynamic coefficient. Graphical abstract

Assays of fibrin network properties altered by VKAs in atrial fibrillation – importance of using an appropriate coagulation trigger

2015 ◽  
Vol 113 (04) ◽  
pp. 851-861 ◽  
Author(s):  
Michal Ząbczyk ◽  
Margareta Blombäck ◽  
Jacek Majewski ◽  
Grzegorz Karkowski ◽  
Hakan N. Wallen ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Thrombin Generation ◽  
Vitamin K Antagonists ◽  
International Normalized Ratio ◽  
Clot Lysis ◽  
Flow Measurements ◽  
Fibrin Networks ◽  
Fibrin Network ◽  
Long Term Treatment

SummaryAtrial fibrillation (AF) is a prothrombotic condition, involving increased thrombin generation and fibrinogen concentrations. Vitamin K antagonists (VKAs) prevent arterial thromboembolism if optimal anticoagulation is achieved by individualised drug doses, assessed by determining the Prothrombin time-related International Normalized Ratio (Pt-INR). There is evidence that formation of tight-laced fibrin networks is pathogenic in prothrombotic diseases. This study was performed among AF patients, to test whether long-term treatment with VKAs affects the structure of fibrin networks, and whether the effect is altered by employing different coagulation triggers: exogenous thrombin (1 IU/ml), 10 pM tissue factor (TF) or a commercial Pt-INR reagent (containing 400-fold more TF). In the thrombin-based method, fibrin network porosity (scanning electron microscopy) and liquid permeability (flow measurements) correlated inversely to fibrinogen concentrations, while positive correlations to the degree of anticoagulation were shown with the Pt-INR reagent. In the method with 10 pM TF, the two above relationships were detected, though the influence of Pt-INR was more profound than that of fibrinogen concentrations. Moreover, greater shortening of clot lysis time (CLT) arose from more permeable clots. As a coagulation trigger, 10 pM TF vs exogenous thrombin or the Pt-INR reagent is more informative in reflecting the in vivo process from thrombin generation to fibrin formation. Since fibrin network permeability rose in parallel to elevations of INR and shortening of CLT in AF patients, antithrombotic effects on prevention of thrombotic complications may be achieved from impairment of thrombin generation, resulting in formation of permeable clots susceptible to fibrinolysis.

Hemodynamics in the abdominal aorta: a comparison of in vitro and in vivo measurements

1994 ◽  
Vol 76 (4) ◽  
pp. 1520-1527 ◽  
Author(s):  
J. E. Moore ◽  
S. E. Maier ◽  
D. N. Ku ◽  
P. Boesiger
Keyword(s):  
Abdominal Aorta ◽  
Velocity Profiles ◽  
Flow Reversal ◽  
Infrarenal Aorta ◽  
Complex Flow ◽  
Flow Measurements ◽  
In Vivo Measurements ◽  
Made In

In vivo measurements of blood velocity profiles are difficult to obtain and interpret, since the parameters that govern the normally highly complex flow situation may not be fully quantified or understood at the time of measurement. In vitro flow models have been used often to better understand vascular hemodynamics. The assumptions made in the design of these models limit the applicability of the results. In this study, in vitro flow measurements made in a carefully designed model of the abdominal aorta were compared with in vivo measurements obtained with magnetic resonance imaging. In the suprarenal aorta, the velocity profiles were mostly forward and axisymmetric in both the in vitro and in vivo cases. In the infrarenal aorta, there was extensive flow reversal noted near the posterior wall in both cases. In the aortic bifurcation, two peaks of flow reversal were noted near the lateral posterior walls, and M-shaped velocity profiles were observed in late diastole. The in vitro and in vivo measurements exhibited good qualitative agreement. The in vitro model was accurate in modeling the in vivo hemodynamics of the abdominal aorta. The complex phenomena observed in vivo were explained on the basis of knowledge gained from the in vitro study.

External approach to in vivo force measurement on mitral valve traction suture

2012 ◽  
Vol 45 (5) ◽  
pp. 908-912 ◽  
Author(s):  
Morten O. Jensen ◽  
Henrik Jensen ◽  
Jesper Langhoff Honge ◽  
Nygaard Hans ◽  
J. Michael Hasenkam ◽  
...  
Keyword(s):  
Mitral Valve ◽  
Force Measurement ◽  
External Approach ◽  
Traction Suture

scholarly journals Quantification of coronary microvascular resistance using angiographic images for volumetric blood flow measurement: in vivo validation

2011 ◽  
Vol 300 (6) ◽  
pp. H2096-H2104 ◽  
Author(s):  
Zhang Zhang ◽  
Shigeho Takarada ◽  
Sabee Molloi
Keyword(s):  
Blood Flow ◽  
Swine Model ◽  
Distribution Analysis ◽  
Flow Probe ◽  
Flow Measurements ◽  
First Pass ◽  
Microvascular Resistance ◽  
Time Density ◽  
In Vivo Validation

Structural coronary microcirculation abnormalities are important prognostic determinants in clinical settings. However, an assessment of microvascular resistance (MR) requires a velocity wire. A first-pass distribution analysis technique to measure volumetric blood flow has been previously validated. The aim of this study was the in vivo validation of the MR measurement technique using first-pass distribution analysis. Twelve anesthetized swine were instrumented with a transit-time ultrasound flow probe on the proximal segment of the left anterior descending coronary artery (LAD). Microspheres were injected into the LAD to create a model of microvascular dysfunction. Adenosine (400 μg·kg−1·min−1) was used to produce maximum hyperemia. A region of interest in the LAD arterial bed was drawn to generate time-density curves using angiographic images. Volumetric blood flow measurements (Qa) were made using a time-density curve and the assumption that blood was momentarily replaced with contrast agent during the injection. Blood flow from the flow probe (Qp), coronary pressure (Pa), and right atrium pressure (Pv) were continuously recorded. Flow probe-based normalized MR (NMRp) and angiography-based normalized MR (NMRa) were calculated using Qp and Qa, respectively. In 258 measurements, Qa showed a strong correlation with the gold standard Qp (Qa = 0.90 Qp + 6.6 ml/min, r2 = 0.91, P < 0.0001). NMRa correlated linearly with NMRp (NMRa = 0.90 NMRp + 0.02 mmHg·ml−1·min−1, r2 = 0.91, P < 0.0001). Additionally, the Bland-Altman analysis showed a close agreement between NMRa and NMRp. In conclusion, a technique based on angiographic image data for quantifying NMR was validated using a swine model. This study provides a method to measure NMR without using a velocity wire, which can potentially be used to evaluate microvascular conditions during coronary arteriography.

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