J056022 Estimation of Mass Transfer across the Air-Water Interface in the High Speed Wind Region with Breaking Waves

The kinematics of locomotion was investigated in the aquatic larvae of Dixella aestivalis and Hydrobius fuscipes with the aid of high-speed video recordings. Both insects are able to skate on the surface of the water using the dorso-apical tracheal gill as an adhesive organ or ‘foot’. Progress relies on the variable adhesion of the foot between ‘slide’ and ‘hold’ periods of the locomotory cycle. The flexural body movements underlying skating in D. aestivalis can be derived directly from the figure-of-eight swimming mechanism used in underwater swimming. The latter is shown to be similar to figure-of-eight swimming in chironomid larvae. This study shows how the deployment of a ‘foot’ enables simple side-to-side flexural movements of the body to be converted into effective locomotion at the air-water interface.

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Through-grid wicking enables high-speed cryoEM specimen preparation

Acta Crystallographica Section D Structural Biology ◽

10.1107/s2059798320012474 ◽

2020 ◽

Vol 76 (11) ◽

pp. 1092-1103

Author(s):

Yong Zi Tan ◽

John L. Rubinstein

Keyword(s):

Glass Fiber ◽

High Speed ◽

Protein Complexes ◽

Absorption Capacity ◽

Specimen Preparation ◽

Water Interface ◽

Time Resolved ◽

Glass Fiber Filter ◽

Liquid Absorption ◽

Air Water Interface

Blotting times for conventional cryoEM specimen preparation complicate time-resolved studies and lead to some specimens adopting preferred orientations or denaturing at the air–water interface. Here, it is shown that solution sprayed onto one side of a holey cryoEM grid can be wicked through the grid by a glass-fiber filter held against the opposite side, often called the `back', of the grid, producing a film suitable for vitrification. This process can be completed in tens of milliseconds. Ultrasonic specimen application and through-grid wicking were combined in a high-speed specimen-preparation device that was named `Back-it-up' or BIU. The high liquid-absorption capacity of the glass fiber compared with self-wicking grids makes the method relatively insensitive to the amount of sample applied. Consequently, through-grid wicking produces large areas of ice that are suitable for cryoEM for both soluble and detergent-solubilized protein complexes. The speed of the device increases the number of views for a specimen that suffers from preferred orientations.

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Simulation of Air–Water Interface Effects for High-speed Planing Hull

Journal of Marine Science and Application ◽

10.1007/s11804-020-00172-0 ◽

2020 ◽

Vol 19 (3) ◽

pp. 398-414

Author(s):

Naga Venkata Rakesh Nimmagadda ◽

Lokeswara Rao Polisetty ◽

Anantha Subramanian Vaidyanatha Iyer

Keyword(s):

High Speed ◽

Water Interface ◽

Fluid Forces ◽

Transition Speed ◽

High Speeds ◽

Air Water Interface ◽

Practical Design ◽

Actual Flow ◽

Wetted Surface Area ◽

Interface Effects

Abstract High-speed planing crafts have successfully evolved through developments in the last several decades. Classical approaches such as inviscid potential flow–based methods and the empirically based Savitsky method provide general understanding for practical design. However, sometimes such analyses suffer inaccuracies since the air–water interface effects, especially in the transition phase, are not fully accounted for. Hence, understanding the behaviour at the transition speed is of fundamental importance for the designer. The fluid forces in planing hulls are dominated by phenomena such as flow separation at various discontinuities viz., knuckles, chines and transom, with resultant spray generation. In such cases, the application of potential theory at high speeds introduces limitations. This paper investigates the simulation of modelling of the pre-planing behaviour with a view to capturing the air–water interface effects, with validations through experiments to compare the drag, dynamic trim and wetted surface area. The paper also brings out the merits of gridding strategies to obtain reliable results especially with regard to spray generation due to the air–water interface effects. The verification and validation studies serve to authenticate the use of the multi-gridding strategies on the basis of comparisons with simulations using model tests. It emerges from the study that overset/chimera grids give better results compared with single unstructured hexahedral grids. Two overset methods are investigated to obtain reliable estimation of the dynamic trim and drag, and their ability to capture the spray resulting from the air–water interaction. The results demonstrate very close simulation of the actual flow kinematics at steady-speed conditions in terms of spray at the air–water interface, drag at the pre-planing and full planing range and dynamic trim angles.

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