The drag coefficient of cased caddis larvae from running waters: experimental determination and ecological applications (original) (raw)
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Journal of Experimental Biology, 2003
Understanding how the shape and motion of an aquatic animal affects the performance of swimming requires knowledge of the fluid forces that generate thrust and drag. Despite recent advances towards understanding the biomechanics of locomotion (see for a review), these forces are poorly understood in swimming animals that are a few millimeters in length. The large diversity of larval fish and marine invertebrates at this scale generate hydrodynamic force that is dependent on both the viscosity and the inertia of the surrounding water. To understand the relative contribution of inertial and viscous forces to the generation of thrust and drag, theoretical models have been developed for the hydrodynamics of swimming at this scale (e.g. . However, little experimental work has attempted to test or refine these theories (exceptions include Fuiman and Batty, 1997;. The goal of the present study was to test hydrodynamic theory by comparing the predictions of theoretical models with measurements of the speed of freely swimming animals and the forces generated by tethered animals.
Science China Technological Sciences
In the last decades, surface drag reduction has been re-emphasized because of its practical values in engineering applications, including vehicles, aircrafts, ships, and fuel pipelines. The bionic study of drag reduction has been attracting scholars' attentions. Here, it was determined that the delicate microstructures on the scales of the fish Ctenopharyngodon idellus exhibit remarkable drag-reduction effect. In addition, the underlying drag-reduction mechanism was carefully investigated. First, exceptional morphologies and structures of the scales were observed and measured using a scanning electron microscope and 3-dimensional (3D) microscope. Then, based on the acquired data, optimized 3D models were created. Next, the mechanism of the water-trapping effect of these structures was analyzed through numerical simulations and theoretical calculations. It was determined that there are many microcrescent units with certain distributions on its surface. In fact, these crescents are effective in generating the "water-trapping" effect and forming a fluid-lubrication film, thus reducing the skin friction drag effectively. Contrasting to a smooth surface, the dynamics finite-element analysis indicated that the maximum drag-reduction rate of a bionic surface is 3.014% at 0.66 m/s flow rate. This study can be used as a reference for an in-depth analysis on the bionic drag reduction of boats, underwater vehicles, and so forth.
Hydrobiologia
By studying hydraulic stress parameters of larvae of the cased caddisfly Drusus biguttatus (Pictet, 1834) in a tributary of the Schwarze Sulm (Carinthia, Austria), we aimed on (1) detecting the flow properties of the spatio-temporally filtered velocity measurements taken, and (2) on defining the hydraulic niche of this caddisfly larva. For this, we took 31 measurement series lasting 30 to 300 s, yielding 2176 single velocity measurements. The probability density functions of the 31 data series were Gaussian or sub-Gaussian, and the mean recurrent interval between velocity maxima within a data series was only 15.00 s. As a consequence, the Trichoptera larvae studied have to face strong flow accelerations in short intervals which is a much higher stress than conventional mean velocity measurements would suggest. The hydraulic niche of Drusus biguttatus is defined by instantaneous flow velocities ranging from 0.04 to 0.69 m s-1 , by drag forces from 13 9 10-6 to 3737 9 10-6 N, by Froude numbers from 0.13 to 1.20, and mostly by Reynolds numbers [ 2000. Under such conditions, only 5.1% of the drag force is compensated by submerged weight,
Development an Experimental Method to Investigate Hydrodynamic Drag
2018
Newcastle University [UNEW] has enhanced the test section of their existing water channel facility. The new measurement section is utilized to measure pressure drop (and hence frictional drag) across a standard flat test panel (length=0.6 m; width=0.22 m). The panel can be tested as cleanly coated as well as exposed to light biofilm growth. Based on measured pressure gradients, the skin friction coefficients of these surfaces are calculated and compared with other well-established methods (i.e., measuring the boundary layer of similar surfaces using a [LDV] system in UNEW's Emerson Cavitation Tunnel [ECT], to evaluate the pressure drop methodology. This paper presents a design and calibration of a flow cell to investigate skin-friction of three different surfaces in a fully developed turbulent flow.
Water
Experiments in a laboratory tank have provided measurements of the normal and tangential drag forces exerted on flat nets for different flow conditions. From those forces, normal and tangential drag coefficients of the nets have been obtained as functions of the Reynolds number and the solidity index. The experiments used two types of nets employed in the operation of a cultivation center: the fish net and the sea lion net, for the clean situation and for real operating conditions, with fouling adhered to the nets. Polyethylene ropes were used to characterize the presence of fouling in the nets. The experiments were carried out to determine equations for the normal and tangential drag coefficients. For the normal drag coefficient, the equations are linear with the Reynolds number, and the coefficients of the equations are linear with the solidity index. The equations are not so accurate for the tangential drag coefficient. The Reynolds number is not a relevant parameter for this coe...
Journal of Experimental Biology, 2010
The lateral line system detects water flow, which allows fish to orient their swimming with respect to hydrodynamic cues. However, it is unclear whether this sense plays a role in the control of propulsion. Hydrodynamic theory suggests that fish could reduce drag by coordinating the motion of the head relative to detected flow signals. To test this hypothesis, we performed measurements of undulatory kinematics during steady swimming in the golden shiner (Notemigonus crysoleucas) at three speeds (4.5, 11.0 and 22.0cms -1 ). We found that the phase shift between yaw angle and lateral velocity (20.5±13.1deg., N5) was significantly greater than the theoretical optimum (0deg.) and the amplitude of these variables created a hydrodynamic index (H0.05±0.03, N6) that was less than an order of magnitude below the theoretical prediction. Furthermore, we repeated these measurements after pharmacologically ablating the lateral line hair cells and found that drag reduction was not adversely influenced by disabling the lateral line system. Therefore, flow sensing does not facilitate active drag reduction. However, we discovered that ablating the lateral line causes the envelope of lateral displacement to nearly double at the envelope's most narrow point for swimming at 4.5cms -1 . Therefore, fish may use hydrodynamic sensing to modulate the lateral amplitude of slow undulatory swimming, which could allow rapid responses to changes in environmental flow.
River Research and Applications, 2011
The restoration of fish passage has been focused on anadromous fish species, whilst studies accommodating passage of coarse species have often been considered incidental, yet frequently these are the predominant group of species encountered in rivers. In addition, fishway designs depend greatly on the interplay between hydraulics and biomechanics, yet very little data are available on the responses to specific hydraulic settings for these species. This study aims to explore the effects of water velocity and turbulence on the behaviour of a cyprinid species -the Iberian barbel Luciobarbus bocagei (Steindachner, 1864) -particularly their upstream movements upon different discharges (38.5 to 77.0 L Á s À1 ), through an indoor full scale pool-type fishway prototype. Larger adults had a higher passage success (mean ¼ 79%) and took less time (mean AE SD (min): 5.7 AE 1.3) to negotiate the entire six pool fishway, when compared to small adults. Correlation analysis between hydraulic variables and fish transit time yielded different results. Correlations were found to be the highest between the horizontal component of Reynolds shear stress and fish transit time, particularly for smaller size-individuals (r ¼ À0.45; p < 0.001), highlighting this variable as a key-parameter which strongly determines the movements of Iberian barbel. The present study identified key factors on Iberian barbel movements that may have direct application to future fishway designs for this species and for other 'weak' swimmers. Figure 2. Plane velocity field in the pools for Q ¼ 47.5 L Á s À1 : (a) z ¼ 0.25 h m ; (b) z ¼ 0.50 h m ; (c) z ¼ 0.80 h m . Flow from the orifice enters at the bottom left of the diagram
Investigation of Hydrodynamic Drag in a Swimming Squid
2014
In this study, hydrodynamic drag on an adult squid was investigated during its fast swimming phase. Numerical model has been generated from a real squid’s computer tomography images. It has been documented that squids can typically swim at velocities from 3.21 m/s to 9.23 m/s under the water. Therefore, by considering the flow on squid’s surface and behind the squid, variation of drag coefficients (at these velocities) has been studied for the squid having about 7.58 fineness ratio. It has been noted that streamlined shape of the squid affects drag force associated with total wetted surface area and flow separation; more specifically, streamlined shape both helps to have delayed flow separation and in return to have lower drag coefficient