Hydrodynamics of flexible fins propelled in tandem, diagonal, triangular and diamond configurations

2018 ◽  
Vol 840 ◽  
pp. 154-189 ◽  
Author(s):  
Sung Goon Park ◽  
Hyung Jin Sung
Keyword(s):  
Immersed Boundary Method ◽  
Leading Edge ◽  
Input Power ◽  
Immersed Boundary ◽  
Diamond Formation ◽  
Propulsive Efficiency ◽  
Fish Schools ◽  
Fluid Environment ◽  
Dimensional Simulation ◽  
Surrounding Fluid

A fish may gain hydrodynamic benefits from being a member of a school. Inspired by fish schools, a two-dimensional simulation was performed for flexible fins propelled in tandem, diagonal, triangular and diamond configurations. The flow-mediated interactions between the flexible fins were analysed by using an immersed boundary method. A transverse heaving motion was prescribed on the leading edge of each fin, and other posterior parts passively adapted to the surrounding fluid as a result of the fluid–flexible-body interaction. The flexible fins were allowed to actively adjust their relative positions in the horizontal direction. The four basic stable configurations are spontaneously formed and self-sustained purely by the vortex–vortex and vortex–body interactions. The hydrodynamic benefits depend greatly on the local positions of the members. For the same heaving motion prescribed on the leading edge, the input power of the following fin in the stable tandem and diagonal configurations is lower by 14 % and 6 %, respectively, than that of the leading fin. The following fin in the diagonal formation can keep pace with the leading fin even for reduced heaving amplitudes because of the help of the leader via their shared fluid environment, where its required input power is reduced by 21 %. The heaving amplitudes of the trailing fins are reduced to optimize the propulsive efficiency, and the average efficiencies in the triangular and diamond configurations increase by up to 14 % and 19 %, respectively, over that of the isolated swimmer. The propulsive efficiencies are enhanced by 22 % for the fins in the second row and by 36 % for the fin in the third row by decreasing the heaving amplitude in the diamond formation.

Modeling Insect Filiform Hair Motion Using the Penalty Immersed Boundary Method

2007 ◽  
Author(s):  
Toma´sˇ Gedeon ◽  
Jeff J. Heys ◽  
B. C. Knott ◽  
Jonas Mulder-Rosi
Keyword(s):  
Immersed Boundary Method ◽  
Immersed Boundary ◽  
Boundary Method ◽  
Wide Range ◽  
Fluid Environment ◽  
Induced Motion ◽  
Acheta Domestica ◽  
Model Equations ◽  
Surrounding Fluid ◽  
Filiform Hair

Many insects are able to sense their surrounding fluid environment through induced motion of their filiform hairs. The mechanism by which the insect can sense a wide range of input signals using the canopy of filiform hairs of different length and orientation is of great interest. Most of the previous filiform hair models have focused on a single, rigid hair in an idealized air field. We have developed [1] a model for a canopy of filiform hairs that are mechanically coupled to the surrounding air. The model equations are based on the penalty immersed boundary method. The key difference between the penalty immersed boundary method and the traditional immersed boundary method is the addition of forces to account for density differences between the immersed solid (the filiform hairs) and the surrounding fluid (air). In this work we validate the model by comparing the model predictions to experimental results on cricket Acheta domestica cercal system.

scholarly journals A Stress Mapping Immersed Boundary Method for Viscous Flows

2021 ◽  
Vol 87 (3) ◽  
pp. 1-20
Author(s):  
Karim M. Ali ◽  
Mohamed Madbouli ◽  
Hany M. Hamouda ◽  
Amr Guaily
Keyword(s):  
Immersed Boundary Method ◽  
Stokes Equations ◽  
Cross Flow ◽  
Navier Stokes ◽  
Immersed Boundary ◽  
Element Formulation ◽  
Navier Stokes Equations ◽  
Boundary Method ◽  
Background Grid ◽  
Dimensional Simulation

This work introduces an immersed boundary method for two-dimensional simulation of incompressible Navier-Stokes equations. The method uses flow field mapping on the immersed boundary and performs a contour integration to calculate immersed boundary forces. This takes into account the relative location of the immersed boundary inside the background grid elements by using inverse distance weights, and also considers the curvature of the immersed boundary edges. The governing equations of the fluid mechanics are solved using a Galerkin-Least squares finite element formulation. The model is validated against a stationary and a vertically oscillating circular cylinder in a cross flow. The results of the model show acceptable accuracy when compared to experimental and numerical results.

scholarly journals Fluid Dynamics of Ballistic Strategies in Nematocyst Firing

Fluids ◽  
2020 ◽  
Vol 5 (1) ◽  
pp. 20 ◽  
Author(s):  
Christina Hamlet ◽  
Wanda Strychalski ◽  
Laura Miller
Keyword(s):  
Immersed Boundary Method ◽  
Short Distance ◽  
Reynolds Numbers ◽  
Two Dimensions ◽  
Immersed Boundary ◽  
Small Scale ◽  
Viscous Damping ◽  
Final Velocity ◽  
Inertial Regime ◽  
Surrounding Fluid

Nematocysts are stinging organelles used by members of the phylum Cnidaria (e.g., jellyfish, anemones, hydrozoans) for a variety of important functions including capturing prey and defense. Nematocysts are the fastest-known accelerating structures in the animal world. The small scale (microns) coupled with rapid acceleration (in excess of 5 million g) present significant challenges in imaging that prevent detailed descriptions of their kinematics. The immersed boundary method was used to numerically simulate the dynamics of a barb-like structure accelerating a short distance across Reynolds numbers ranging from 0.9–900 towards a passive elastic target in two dimensions. Results indicate that acceleration followed by coasting at lower Reynolds numbers is not sufficient for a nematocyst to reach its target. The nematocyst’s barb-like projectile requires high accelerations in order to transition to the inertial regime and overcome the viscous damping effects normally encountered at small cellular scales. The longer the barb is in the inertial regime, the higher the final velocity of the projectile when it touches its target. We find the size of the target prey does not dramatically affect the barb’s approach for large enough values of the Reynolds number, however longer barbs are able to accelerate a larger amount of surrounding fluid, which in turn allows the barb to remain in the inertial regime for a longer period of time. Since the final velocity is proportional to the force available for piercing the membrane of the prey, high accelerations that allow the system to persist in the inertial regime have implications for the nematocyst’s ability to puncture surfaces such as cellular membranes or even crustacean cuticle.

Actively flapping tandem flexible flags in a viscous flow

2015 ◽  
Vol 780 ◽  
pp. 120-142 ◽  
Author(s):  
Emad Uddin ◽  
Wei-Xi Huang ◽  
Hyung Jin Sung
Keyword(s):  
Viscous Flow ◽  
Immersed Boundary Method ◽  
Leading Edge ◽  
Underlying Mechanism ◽  
The Body ◽  
Immersed Boundary ◽  
Flexible Body ◽  
Flexible Bodies ◽  
Body Shapes ◽  
Heave Motion

The active flapping motions of fish and cetaceans generate both propulsive and manoeuvring forces. The tail fin motions of the majority of fish can essentially be viewed as a combined pitch-and-heave motion. Downstream bodies are strongly influenced by the vortices shed from an upstream body. To investigate the interactions between flexible bodies and vortices, the present study examined tandem flexible flags in a viscous flow by using an improved version of the immersed boundary method. The upstream flag underwent passive flapping in a uniform flow while the downstream flag flapped according to a prescribed pitching and heaving motion of the leading edge. The influences of the active flapping motion on the system dynamics were examined in detail, including the frequency, the phase angle, the bending coefficient and the amplitudes of the pitching and heaving motion. The variation of the drag coefficient of the downstream flag was explored together with the instantaneous vorticity contours and the body shapes. Both the slalom mode and the interception mode were identified according to the vortex–flexible body interactions, corresponding to the low- and high-drag situations, respectively. The underlying mechanism was discussed and compared with previous studies.

APPLICATION OF IMMERSED BOUNDARY METHOD ON INSTRUMENTED TURBINE BLADE WITH LES

2021 ◽  
pp. 1-11
Author(s):  
Bryn N Ubald ◽  
Rob Watson ◽  
Jiahuan Cui ◽  
Paul G. Tucker ◽  
Shahrokh Shahpar
Keyword(s):  
Immersed Boundary Method ◽  
Pressure Loss ◽  
Turbine Blades ◽  
Leading Edge ◽  
Immersed Boundary ◽  
Eddy Simulation ◽  
Boundary Method ◽  
Flow Features ◽  
Compressor And Turbine Blades ◽  
High Level

Abstract Leading edge instrumentation used in compressor and turbine blades for jet-engine test rigs can cause significant obstruction and lead to a marked increase in downstream pressure loss. Typical instrumentation used in such a scenario could be a Kiel shrouded probe with either a thermocouple or pitot-static tube for temperature/pressure measurement. High fidelity analysis of a coupled blade and probe requires the generation of a high-quality mesh which can take a significant amount of an engineer's time. The application of Immersed Boundary Method (IBM) and Large Eddy Simulation is shown in this paper to enable the use of an extremely simple mesh to observe the primary flow features generated due to the blade and probe interaction effects, as well as quantify downstream pressure loss to within a high level of accuracy. IBM is utilised to approximately model the probe, while fully resolving the blade itself through a series of LES simulations. This method has shown to be able to capture downstream loss profiles as well as integral quantities compared to both experiment and fully wall resolved LES without the need to spend a significant amount of time generating the ideal mesh. Additionally, it is also able to capture the turbulence anisotropy surrounding the probe and blade regions.

Application of Immersed Boundary Method on Instrumented Turbine Blade With LES

2020 ◽  
Author(s):  
Bryn N. Ubald ◽  
Rob Watson ◽  
Jiahuan Cui ◽  
Paul Tucker ◽  
Shahrokh Shahpar
Keyword(s):  
Immersed Boundary Method ◽  
Pressure Loss ◽  
Turbine Blades ◽  
Leading Edge ◽  
Immersed Boundary ◽  
Eddy Simulation ◽  
Boundary Method ◽  
Flow Features ◽  
Compressor And Turbine Blades ◽  
High Level

Abstract Leading edge instrumentation used in compressor and turbine blades for jet-engine test rigs can cause significant obstruction and lead to a marked increase in downstream pressure loss. Typical instrumentation used in such a scenario could be a Kiel-shrouded probe with either a thermocouple or pitot-static tube for temperature/pressure measurement. High fidelity analysis of a coupled blade and probe requires the generation of a high quality mesh which can take a significant amount of an engineers time. The application of Immersed Boundary Method (IBM) and Large Eddy Simulation is shown in this paper to enable the use of an extremely simple mesh to observe the primary flow features generated due to the blade and probe interaction effects, as well as quantify downstream pressure loss to within a high level of accuracy. IBM is utilised to approximately model the probe, while fully resolving the blade itself through a series of LES simulations. This method has shown to be able to capture downstream loss profiles as well as integral quantities compared to both experiment and fully wall-resolved LES without the need to spend a significant amount of time generating the ideal mesh. Additionally, it is also able to capture the turbulence anisotropy surrounding the probe and blade regions.

Wake Structures and Effect of Hydrofoil Shapes in Efficient Flapping Propulsion

2021 ◽  
Author(s):  
John Kelly ◽  
Pan Han ◽  
Haibo Dong ◽  
Tyler Van Buren
Keyword(s):  
Shape Change ◽  
Leading Edge ◽  
Chord Length ◽  
Immersed Boundary ◽  
Shape Transformation ◽  
Propulsive Efficiency ◽  
Favorable Pressure Gradient ◽  
Edge Vortex ◽  
And Performance ◽  
Numerical Solver

Abstract In this work, direct numerical simulation (DNS) is used to investigate how airfoil shape affects wake structure and performance during a pitching-heaving motion. First, a class-shape transformation (CST) method is used to generate airfoil shapes. CST coefficients are then varied in a parametric study to create geometries that are simulated in a pitching and heaving motion via an immersed boundary method-based numerical solver. The results show that most coefficients have little effect on the propulsive efficiency, but the second coefficient does have a very large effect. Looking at the CST basis functions shows that the effect of this coefficient is concentrated near the 25% mark of the foils chord length. By observing the thrust force and hydrodynamic power through a period of motion it is shown that the effect of the foil shape change is realized near the middle of each flapping motion. Through further inspection of the wake structures, we conclude that this is due to the leading-edge vortex attaching better to the foil shapes with a larger thickness around 25% of the chord length. This is verified by the pressure contours, which show a lower pressure along the leading edge of the better performing foils. The more favorable pressure gradient generated allows for higher efficiency motion.

Vortex interaction between two tandem flexible propulsors with a paddling-based locomotion

2016 ◽  
Vol 793 ◽  
pp. 612-632 ◽  
Author(s):  
Sung Goon Park ◽  
Hyung Jin Sung
Keyword(s):  
Phase Difference ◽  
Immersed Boundary Method ◽  
Propulsion System ◽  
Immersed Boundary ◽  
Vortex Interaction ◽  
Flexible Bodies ◽  
Tandem Configuration ◽  
Boundary Method ◽  
The Cost ◽  
Surrounding Fluid

Schooling behaviours among self-propelled animals can benefit propulsion. Inspired by the schooling behaviours of swimming jellyfish, flexible bodies that self-propel through a paddling-based motion were modelled in a tandem configuration. This present study explored the hydrodynamic patterns generated by the interactions between two flexible bodies and the surrounding fluid in the framework of the penalty immersed boundary method. The hydrodynamic patterns produced in the wake revealed flow-mediated interactions between two tandem propulsors, including vortex–vortex and vortex–body interactions. Two tandem flexible propulsors paddling with identical amplitude and frequency produced stable configurations as a result of the flow-mediated interactions. Both the upstream and downstream propulsors benefited from the tandem configuration in terms of the locomotion velocity and the cost, compared with an isolated propulsion system. The interactions were examined as a function of the initial gap distance and the phase difference in the paddling frequency. The equilibrium gap distance between two propulsors remained constant, regardless of the initial gap distance, although it did depend on the phase difference in the paddling frequency.

scholarly journals Three-dimensional simulation for fast forward flight of a calliope hummingbird

2016 ◽  
Vol 3 (6) ◽  
pp. 160230 ◽  
Author(s):  
Jialei Song ◽  
Bret W. Tobalske ◽  
Donald R. Powers ◽  
Tyson L. Hedrick ◽  
Haoxiang Luo
Keyword(s):  
Immersed Boundary Method ◽  
High Speed ◽  
Computational Study ◽  
Three Dimensional ◽  
The Body ◽  
Immersed Boundary ◽  
Forward Flight ◽  
Advance Ratio ◽  
Dimensional Simulation ◽  
Thrust Production

We present a computational study of flapping-wing aerodynamics of a calliope hummingbird ( Selasphorus calliope ) during fast forward flight. Three-dimensional wing kinematics were incorporated into the model by extracting time-dependent wing position from high-speed videos of the bird flying in a wind tunnel at 8.3 m s −1 . The advance ratio, i.e. the ratio between flight speed and average wingtip speed, is around one. An immersed-boundary method was used to simulate flow around the wings and bird body. The result shows that both downstroke and upstroke in a wingbeat cycle produce significant thrust for the bird to overcome drag on the body, and such thrust production comes at price of negative lift induced during upstroke. This feature might be shared with bats, while being distinct from insects and other birds, including closely related swifts.

scholarly journals Margination and adhesion dynamics of tumor cells in a real microvascular network

2021 ◽  
Vol 17 (2) ◽  
pp. e1008746
Author(s):  
Sitong Wang ◽  
Ting Ye ◽  
Guansheng Li ◽  
Xuejiao Zhang ◽  
Huixin Shi
Keyword(s):  
Blood Flow ◽  
Tumor Cells ◽  
Immersed Boundary Method ◽  
Tumor Metastasis ◽  
Dissipative Particle Dynamics ◽  
Three Dimensional ◽  
Immersed Boundary ◽  
Microvascular Network ◽  
Adhesion Behavior ◽  
Dimensional Simulation

In tumor metastasis, the margination and adhesion of tumor cells are two critical and closely related steps, which may determine the destination where the tumor cells extravasate to. We performed a direct three-dimensional simulation on the behaviors of the tumor cells in a real microvascular network, by a hybrid method of the smoothed dissipative particle dynamics and immersed boundary method (SDPD-IBM). The tumor cells are found to adhere at the microvascular bifurcations more frequently, and there is a positive correlation between the adhesion of the tumor cells and the wall-directed force from the surrounding red blood cells (RBCs). The larger the wall-directed force is, the closer the tumor cells are marginated towards the wall, and the higher the probability of adhesion behavior happen is. A relatively low or high hematocrit can help to prevent the adhesion of tumor cells, and similarly, increasing the shear rate of blood flow can serve the same purpose. These results suggest that the tumor cells may be more likely to extravasate at the microvascular bifurcations if the blood flow is slow and the hematocrit is moderate.

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