The journal retracts the article titled “Experimental Investigation of the Effects of Grooves in Fe2O4/Water Nanofluid Pool Boiling” [...]
Ray-like swimmers achieve propulsion through undulatory pectoral-fin motions, but the hydrodynamic consequences of these prescribed motions remain incompletely understood. We investigated a bio-inspired ray model that combines geometry reconstructed from a Javan cownose ray (Rhinoptera javanica) with pectoral-fin kinematics parameterized from published manta and mobuliform swimming studies. Pectoral-fin deformation was prescribed using analytical amplitude and phase functions, while fluid forces updated only streamwise rigid-body translation. The model yielded a maximum hydrodynamic Froude efficiency of 47.4% under the prescribed kinematics, and mean speed increased approximately linearly with flapping frequency over the retained 0.2–0.6 Hz range (R2 = 0.9890). The surface-attached vortex became less continuous as frequency increased, while pressure evolution indicated that thrust arose mainly during downstrokes. These results characterize the hydrodynamic response of this hybrid, bio-inspired ray model to the imposed manta-like waveform; they are not species-specific predictions for manta rays or R. javanica.
As the core of the thermal management system in new energy vehicles, the operational reliability of electronic water pumps directly affects vehicle thermal safety. Radial force and pressure pulsation, as key indicators, significantly impact the operation of the rotor system in electronic water pumps. However, existing research has largely focused on optimizing blade structures, with limited consideration of how front cavity clearance affects radial force and pressure pulsation. Therefore, this paper investigates the effect of front cavity clearance on the radial force and pressure pulsation of electronic water pumps through numerical simulation. The results show that under steady-state conditions, changes in the front cavity clearance significantly affect the external characteristics. Specifically, efficiency increases with the enlargement of the front cavity clearance, up to 3.5%. The variation in head is related to the flow rate: at high flow rates, it increases with the clearance, peaking at 3.5%, while at low flow rates, it decreases by up to 1.4%. The impact on impeller forces is more pronounced. Radial force decreases by up to 54.2% with larger clearance, while axial force shows the opposite trend, increasing by 202.8%. Under unsteady-state conditions, increasing the front cavity clearance dampens both radial force by up to 49.4% and pressure pulsation. The maximum 30.2% reduction in pressure pulsation. This study provides an effective tool for investigating the unsteady characteristics of electronic water pumps and offers theoretical support for suppressing radial force and pressure pulsation.
In this study, we proposed and evaluated a new dielectrophoresis (DEP)-based device for the high-throughput, non-invasive separation of cells with similar physical properties. Although DEP is an established technology for separating biological particles based on their dielectric properties, the accurate separation of populations of similar cell types—such as normal cells and cancer cells of the same species—remains a significant technical challenge. In this study, separation experiments using a prototype device were conducted with normal (MCF10A) and tumor (MDA-MB-231) human mammary cells. The experiments systematically analyzed the effects of three key parameters—A.C. frequency (f), flow rate (Q), and solution conductivity (σf)—on the cell separation ratio (Φ). The experimental results identified optimal operating conditions at f = 57.6 kHz, Q = 5.0 mL/h, and σf = 40 mS/m, achieving a maximum separation ratio of Φ = 72.1%. These findings demonstrate that the potential of this device to perform high-speed processing without the need for fluorescent labeling or invasive pretreatment. This study provides a fundamental framework for optimizing DEP parameters and outlines a pathway toward more efficient clinical applications and the isolation of rare cell populations.
How an airfoil generates lift is settled engineering practice—the Kutta–Joukovsky theorem relates lift to circulation, and the Kutta condition selects the observed flow—yet why the Kutta condition holds has again become a subject of discussion: since 2022 a variational theory of lift has proposed an inviscid selection principle based on Gauss’s principle of least constraint, prompting an ongoing debate in the archival literature. This review reassembles, in a self-contained way, the viscous answer given by matched asymptotic expansions. Three questions organise the presentation: what inviscid theory leaves undetermined and the logical status of the Kutta condition within it (Q1); whether boundary-layer theory and its higher-order completion, triple-deck theory, provide a deductive route from the Navier–Stokes equations to the Kutta condition together with quantitative predictions (Q2); and what this viscous route implies for the proposed inviscid selection principles (Q3). Starting from Blasius’ flat-plate solution and Goldstein’s near-wake, the triple-deck structure of the trailing-edge region is developed, and the resulting first-order corrections—the flat-plate drag correction and the lift-slope reduction cL/(2πα)=1−B with B=a1λ−5/4Re−3/8—are compared with wind-tunnel data, XFOIL and laminar Navier–Stokes solutions: the drag correction is confirmed quantitatively, the lift correction in sign, trend and order of magnitude over two decades of Reynolds number, and the domain of validity of the laminar theory is stated explicitly. The wake, with its transversely continuous pressure, enforces pressure continuity at the trailing edge and thereby fixes circulation and lift; any inviscid selection principle is constrained to reproduce this asymptotic limit. The viscous treatment of rounded trailing edges (Sychev–Smith separation combined with the Howarth–Sears wake condition) is outlined, and for bodies with smooth trailing edges a three-way quantitative test (variational vs. interactive boundary-layer/triple-deck vs. Navier–Stokes) is proposed, two legs of which already exist in the literature.
