Biomechanics of rheotaxis in six teleost genera

2006 ◽  
Vol 84 (8) ◽  
pp. 1173-1186 ◽  
Author(s):  
Robert W. Blake
Keyword(s):  
Lift Coefficient ◽  
Body Width ◽  
Total Length ◽  
Morphological Adaptations ◽  
Maximal Height ◽  
Dead Fish ◽  
Optimal Values ◽  
Lift And Drag ◽  
Frictional Coefficients ◽  
First Time

Biomechanical, behavioural, and morphological adaptations affecting lift and drag on tropical stream fish (five loricariids and one gyrinocheilid) are analyzed. The drag on fish attached to a surface is directly measured for the first time, allowing the lift coefficient to be inferred. Mean drag coefficients (0.2–0.9, based on projected frontal area) are 2 to 30 times the equivalent frictional coefficients for laminar flow for smooth blisters attached to a surface. Fineness ratios (total length / maximal height, l/h = 6.7–9.0), flattening (maximal body width / maximal height, b/h = 0.9–2.0), and lengthening (distance from end of rostrum to maximal height / total length, x/l = 0.17–0.22) are similar to optimal values for technical bodies of low drag (smooth blisters attached to surfaces: 10, 2, and 0.3 for l/h, b/h, and x/l, respectively). The station-holding ability of Gyrinocheilus aymonieri (Tirant, 1883) (closed oral sucker) is compared with that of the loricariids (open oral suckers) using live and dead slipping velocities (Vlive and Vdead; water velocity at which live and dead fish first move backwards against the current, respectively) measured on a smooth Perspex® surface. Gyrinocheilus aymonieri has the greatest station-holding ability (Vlive = 59.1 cm·s–1, Vlive – Vdead = 45.7 cm·s–1). Fish with high Vdead and low Vlive – Vdead values rely more on frictional devices (e.g., spines and odontodes) for station-holding than on oral suction (e.g., fish of the genera Otocinclus Cope, 1871 and Hypostomus Lacépède, 1803), whereas those with low Vdead and high Vlive – Vdead values place a greater emphasis on suction (e.g., G. aymonieri and the genus Pterygoplichthys Gill, 1858). Stream fishes maximize slipping speed through high densities (1.06–1.15 g·cm–3), high frictional coefficients (0.12–1.2 on a Perspex® surface), and high rheotactic suction pressures (26–173 Pa). In addition, a negative lift coefficient of –0.5 is calculated for the genus Chaetostoma von Tschudi, 1846.

scholarly journals Ecological Observations on Hybrid Populations of European Plethodontid Salamanders, Genus Speleomantes

Diversity ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 285
Author(s):  
Enrico Lunghi ◽  
Fabio Cianferoni ◽  
Stefano Merilli ◽  
Yahui Zhao ◽  
Raoul Manenti ◽  
...  
Keyword(s):  
Body Condition ◽  
Parental Species ◽  
Stomach Contents ◽  
Trophic Niche ◽  
Natural Hybrid ◽  
Ecological Information ◽  
Total Length ◽  
Plethodontid Salamanders ◽  
The Future ◽  
First Time

Speleomantes are the only plethodontid salamanders present in Europe. Multiple studies have been performed to investigate the trophic niche of the eight Speleomantes species, but none of these studies included hybrid populations. For the first time, we studied the trophic niche of five Speleomantes hybrid populations. Each population was surveyed twice in 2020, and stomach flushing was performed on each captured salamander; stomach flushing is a harmless technique that allows stomach contents to be inspected. We also assessed the potential divergence in size and body condition between natural and introduced hybrids, and their parental species. Previously collected data on Speleomantes were included to increase the robustness of these analyses. In only 33 out of 134 sampled hybrid Speleomantes we recognized 81 items belonging to 11 prey categories. The frequency of empty stomachs was higher in females and individuals from natural hybrid populations, whereas the largest number of prey was consumed by males. We compared the total length and body condition of 685 adult salamanders belonging to three types of hybrids and three parental (sub)species. Three group of salamanders (one hybrid and two parental species) showed significantly larger size, whereas no difference in body condition was observed. This study provided novel ecological information on Speleomantes hybrid populations. We also provided insights into the potential divergence between hybrids and parental species in terms of size and body condition. We discuss our findings, and formulate several hypotheses that should be tested in the future.

scholarly journals First record of Dero (Aulophorus) bimagnasetus Harman (Oligochaeta) from Brazil and habitat characteristics

2014 ◽  
Vol 74 (2) ◽  
pp. 483-488
Author(s):  
R. Campitelli-Ramos ◽  
JV. Lucca ◽  
LLD. Oliveira ◽  
MR. Marchese ◽  
O. Rocha
Keyword(s):  
Benthic Communities ◽  
First Record ◽  
Biological Data ◽  
Habitat Characteristics ◽  
Low Oxygen ◽  
Body Width ◽  
Ecological Information ◽  
Freshwater Biota ◽  
Physical And Chemical ◽  
First Time

Annelid worms represent a significant part of freshwater benthic communities worldwide and Oligochaeta is a particularly species-rich group. Dero (A) bimagnasetus (Naididae) previously found and described from a small marsh in Surinam in 1974, has now been found for the first time in Barra Lake, MG, Brazil. Due to the scarce biological data and absence of ecological information in the literature regarding this species we are presenting morphological information on the specimens obtained and the physical and chemical characteristics of the habitat they were found. This species occurred only in the littoral zone of Barra Lake, in muddy, low oxygen, low conductivity and low organic matter sediment. The four individuals collected ranged 3.17-4.15 mm total length; 0.25 - 0.26 mm body width and 0.16-0.21 mm3 total volume. Considering the present anthropic pressures on freshwater biota and fast biodiversity losses worldwide it is now recognized that attention must be paid to low abundance species and the urgency for preservation of their habitats.

Description of the mature larva and pupa of Ora semibrunnea Pic (Coleoptera: Scirtidae) with notes on its biology

Zootaxa ◽  
2019 ◽  
Vol 4551 (1) ◽  
pp. 53 ◽  
Author(s):  
GABRIELLE JORGE ◽  
MARÍA LAURA LIBONATTI ◽  
CESAR JOÃO BENETTI ◽  
NEUSA HAMADA
Keyword(s):  
Water Surface ◽  
Brazilian Amazon ◽  
First Record ◽  
Biological Information ◽  
Mature Larva ◽  
Natural Lakes ◽  
Morphological Adaptations ◽  
Brazilian Amazon Region ◽  
And Behavior ◽  
First Time

In this paper we describe and illustrate for the first time the immature forms (larva and pupa) of Ora semibrunnea Pic, 1922, including biological information and behavior observed in the laboratory. This is the first record of the occurrence of this species in the Brazilian Amazon region. Larvae and pupae were found in natural lakes associated with macrophyte banks. Pupae are aquatic and have morphological adaptations (well-developed pronotal siphons) to obtain atmospheric O2 at the water surface. 

Analysis of Vortex-Induced Vibration of Riser using Spalart-Almaras Model

2014 ◽  
Vol 69 (7) ◽  
Author(s):  
Jaswar Koto ◽  
Abdul Khair Junaidi
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Vortex Shedding ◽  
Lift Coefficient ◽  
Offshore Structures ◽  
The Other ◽  
Main Concern ◽  
Vortex Induced Vibration ◽  
Simulation Results ◽  
Lift And Drag

Vortex-induced vibration is natural phenomena where an object is exposed to moving fluid caused vibration of the object. Vortex-induced vibration occurred due to vortex shedding behind the object. One of the offshore structures that experience this vortex-induced vibration is riser. The riser experience vortex-induced vibration due to vortex shedding caused by external load which is sea current. The effect of this vortex shedding to the riser is fatigue damage. Vortex-induced vibration of riser becomes the main concern in oil and gas industry since there will be a lots of money to be invested for the installation and maintenance of the riser. The previous studies of this vortex-induced vibration have been conducted by experimental method and Computational Fluid Dynamics (CFD) method in order to predict the vortex shedding behaviour behind the riser body for the determination of way to improve the riser design. This thesis represented the analysis of vortex induced vibration of rigid riser in two-dimensional. The analysis is conducted using Computational Fluid Dynamic (CFD) simulations at Reynolds number at 40, 200, 1000, and 1500. The simulations were performed using Spalart-Allmaras turbulent model to solve the transport equation of turbulent viscosity. The simulations results at Reynolds number 40 and 200 is compared with the other studies for the validation of the simulation, then further simulations were conducted at Reynolds number of 1000 and 1500. The coefficient of lift and drag were obtained from the simulations. The comparison of lift and drag coefficient between the simulation results in this study and experiment results from the other studies showed good agreement. Besides that, the in-line vibration and cross-flow vibration at different Reynolds number were also investigated. The drag coefficient obtained from the simulation results remain unchanged as the Reynolds number increased from 200 to 1500. The lift coefficient obtained from the simulations increased as the Reynolds number increased from 40 to 1500.

An Experimental Investigation Assessing the Validity of Quasi-Static Calculations for an Oscillating Hydrofoil

2011 ◽  
Author(s):  
Rajan Fernandez ◽  
Keith Alexander
Keyword(s):  
Steady Flow ◽  
Strouhal Number ◽  
Strong Dependence ◽  
Lift Coefficient ◽  
Experimental Program ◽  
Design Data ◽  
Drag And Lift ◽  
Drag And Lift Coefficient ◽  
Lift And Drag ◽  
Human Powered

Inspired by animals, flapping wing propulsion has been of interest since the early 1900s. Flapping hydrofoil propulsion has been attempted by designers of human powered watercraft because of the novelty and the apparent high theoretical efficiency, but with limited success. The earliest human powered hydrofoil, the Wasserlaufer, was invented by Julius Schuck in 1953. The first really successful human powered hydrofoil, the Trampofoil, was invented by Alexander Sahlin in 1998. While these craft function adequately the design data for flapping hydrofoils is inadequate or not available. This paper describes an experimental program and initial results for the required data. To design a vehicle with a lifting and thrusting oscillating hydrofoil the force that the hydrofoil will exert on the vehicle through its entire oscillating cycle must ideally be known. The force profiles could be estimated via quasi-static calculations based on steady flow lift and drag coefficients, but these often do not cover the full 360 degree range that can be required and there is doubt that the steady flow coefficients properly represent the dynamic situation of an oscillating hydrofoil. Hence a valuable process would be one that could determine dynamic drag and lift coefficient loops as function of the Strouhal number, heaving and pitching profiles. To work toward the collection of this information, experimental data is being recorded in a towing tank with an oscillating NACA4415 hydrofoil over a range of Strouhal numbers and types of oscillating profiles. While there are still some limitations to the experimental equipment preliminary experimental results show the limitations of using quasi-static calculations and go some way to providing the design data for the hydrofoil section tested. We conclude that quasi-static calculations based on the gliding coefficient curve for for an oscillating hydrofoil are only valid for very small Strouhal numbers (St≪0.05). We have shown that as the Strouhal number increases, the error in such calculations increases very rapidly. We also note that the lift coefficient of the hydrofoil has a strong dependence on the angle of attack and is not affected by the gliding stall.

Stability Analysis of a Light Aircraft Configuration Using Computational Fluid Dynamics

2012 ◽  
Vol 225 ◽  
pp. 391-396 ◽  
Author(s):  
Mohammed Mahdi ◽  
Yasser A. Elhassan
Keyword(s):  
Numerical Simulation ◽  
Stokes Equations ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Rate Of Change ◽  
Navier Stokes ◽  
Rolling Moment ◽  
Moment Coefficient ◽  
Stability Derivatives ◽  
Lift And Drag

This work aims to simulate and study the flow field around SAFAT-01 aircraft using numerical solution based on solving Reynolds Averaged Navier-Stokes equations coupled with K-ω SST turbulent model. The aerodynamics behavior of SAFAT-01 aircraft developed at SAFAT aviation complex were calculated at different angles of attack and side slip angles. The x,y and z forces and moments were calculated at flight speed 50m/s and at sea level condition. Lift and drag curves for different angles of attack were plotted. The maximum lift coefficient for SAFAT-01 was 1.67 which occurred at angle of attack 16° and Maximum lift to drag ratio (L/D) was 14 which occurred at α=3°, and the zero lift drag coefficient was 0.0342. Also the yawing moment coefficient was plotted for different side slip angles as well as rolling moment. The longitudinal stability derivatives with respect to angle of attack, speed variation (u), rate of pitch (q) and time rate of change of angle of attack were calculated using obtained CFD results. Concerning lateral stability only side slips derivatives were calculated. To validate this numerical simulation USAF Digital DATCOM is used to analyze this aircraft; a comparison between predicted results for this aircraft and Digital DATCOM indicated that this numerical simulation has high ability for predicting the aerodynamics characteristics.

Drag and lift measurements of solid sports balls in still air

2017 ◽  
Vol 232 (3) ◽  
pp. 255-263 ◽  
Author(s):  
Jeff R Kensrud ◽  
Lloyd V Smith
Keyword(s):  
Surface Roughness ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Rough Surface ◽  
Lift Coefficient ◽  
Laboratory Setting ◽  
Air Drag ◽  
High Speeds ◽  
Drag And Lift ◽  
Lift And Drag

The following article considers lift and drag measurements of solid sports balls propelled through still air in a laboratory setting. The balls traveled at speeds ranging from 26 to 134 m/s with spin rates up to 3900 r/min. Light gates measured the speed and location of the balls at two locations from which lift and drag values were determined. Ball roughness varied from polished to rough surface protrusions, that is, seams as high as 1.5 mm. Lift and drag were observed to depend on speed, spin rate, surface roughness, and seam orientation. A drag crisis was observed on smooth balls as well as non-rotating seamed balls with seam heights less than 0.9 mm. The drag coefficient of approximately 0.42 was nearly constant with speed for spinning seamed balls with seam height greater than 0.9 mm. The still air drag coefficient of smooth balls was comparable to wind tunnel drag at low speeds ( Re < 2 × 105) and higher than wind tunnel results at high speeds ( Re > 2 × 105). The lift and drag coefficients of spinning balls increased with increasing spin rate. The lift coefficient of baseballs was not sensitive to ball orientation or seam height.

Effects of surface flow visualisation on aerodynamic loads at low Reynolds number

2015 ◽  
Vol 119 (1215) ◽  
pp. 663-672
Author(s):  
L. W. Traub ◽  
R. Waghela ◽  
E. M. Botero
Keyword(s):  
Drag Coefficient ◽  
Lift Coefficient ◽  
Time History ◽  
Surface Flow ◽  
Flow Visualisation ◽  
Distribution Method ◽  
History Of ◽  
Low Reynolds ◽  
Lift And Drag ◽  
Lift And Drag Coefficient

AbstractIn this article, the effect of on-surface flow visualisation (SVF) techniques on measured loads over an airfoil are explored. Titanium dioxide based mixture effects on the lift and drag coefficient are experimentally quantified at low Reynolds numbers by recording the time history as the patterns evolve and freeze. With statistical comparison based on Student’s t-distribution method, it was determined that the effect on the drag coefficient was minimal but the lift coefficient was slightly attenuated. Additionally, it was observed that at high angles-of-attack the temporal history of the flow as the wind tunnel ramps up may alter the steady-state flow field in the presence of a SFV mixture.

An experimental investigation of the oscillating lift and drag of a circular cylinder shedding turbulent vortices

1961 ◽  
Vol 11 (2) ◽  
pp. 244-256 ◽  
Author(s):  
J. H. Gerrard
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Cylinder Surface ◽  
Fluctuating Pressure ◽  
Order Of Magnitude ◽  
Lift And Drag

The oscillating lift and drag on circular cylinders are determined from measurements of the fluctuating pressure on the cylinder surface in the range of Reynolds number from 4 × 103 to just above 105.The magnitude of the r.m.s. lift coefficient has a maximum of about 0.8 at a Reynolds number of 7 × 104 and falls to about 0.01 at a Reynolds number of 4 × 103. The fluctuating component of the drag was determined for Reynolds numbers greater than 2 × 104 and was found to be an order of magnitude smaller than the lift.

First record of the marbled spinefoot Siganus rivulatus (Pisces: Siganidae) in the Adriatic Sea

2004 ◽  
Vol 84 (5) ◽  
pp. 1087-1088 ◽  
Author(s):  
J. Dulĉić ◽  
A. Pallaoro
Keyword(s):  
Mediterranean Sea ◽  
Adriatic Sea ◽  
First Record ◽  
Beach Seine ◽  
Total Length ◽  
The Mediterranean ◽  
Siganus Rivulatus ◽  
First Time

Lessepsian migrant Siganus rivulatus is reported for the first time from the Adriatic Sea, substantially further north than its usual area of occurrence in the Mediterranean Sea. Two specimens (111 mm total length [TL] and 149 mm TL) were captured by beach seine on 5 October 2002 off islet Bobara, near Cavtat (southern Adriatic). Morphometric and meristic characteristics of the specimens are provided. The possible explanations of this occurrence are discussed.

Sign in / Sign up

Export Citation Format

Share Document