Nikolai Kornev

Complex numerical modeling of dynamics and crashes of wing-in-ground vehicles

The Wing-In-Ground craft (WIG), a vehicle flying in the ground effect, is a promising transportation means of the near future. This paper describes mathematical modeling of WIG motion in all regimes, such as planing, take-off, transition to flight, and flight itself. The model, which includes nonlinear hydroaerodynamics, serves as a base for simulation of motion. The theory developed here enhances the process of designing WIG vehicles; its advantages and disadvantages are discussed. The results of numerical modeling are compared with experimental data obtained for planing and flight regimes of motion. The model is applied for studying emergency problems in WIG operation.

Complex mathematical model of the WIG motion including the take-off mode

Abstract This paper describes an effort to develop a predictive tool for the design of a new promising marine transport — the WIG craft. The presented mathematical model of the WIG craft is capable of modeling the aerodynamics of a WIG system including the ground effect, the hydrodynamics of a stepped planing hull with a hydrofoil and also the simulation of motion for the craft. Based on extensive experience using the model, it is shown that the most important and necessary features of WIG aero- and hydrodynamics are taken into account. The results of simulations have been validated through comparison with other theoretical approaches and also with model experiments. The mathematical model is applied to investigate the dynamics of the small manually piloted WIG craft: “Hydrowing VT01”. The numerical study resulted in recommendations allowing the pilot to overcome the pitch-up tendency and also to perform the take-off manoeuvre smoothly. The stability of the WIG with a hydrofoil and also the dynamic properties of anti-collision manoeuvres have been studied and are presented.

Synthesis of homogeneous anisotropic divergence-free turbulent fields with prescribed second-order statistics by vortex dipoles

This Communication presents a mathematical procedure for generation of turbulent velocity fields with prescribed shell-summed energy spectra. The velocity field is represented as the sum of velocities induced by a set of randomly distributed vortex dipoles (vortons). Closed-form analytical solutions are found for the inner structure of the vortons from the condition that the shell-summed energy spectrum of the synthesizing field is equal to the prescribed one. The proposed procedure is applied to turbulent fields with the spectrum of the decaying turbulence and the typical velocity energy spectrum of homogeneous turbulence. The solution for decaying turbulence is the exact analytical solution of the Navier-Stokes equation for the turbulent field in the final stage of the decay.

Dynamics and stability of racing boats with air wings

The aim of this paper is to derive a mathematical model for predicting the longitudinal stability of racing boats with aerodynamic support. The theory is based on a combination of stability theories developed for planing boats and wing in ground effect craft. The influence of different geometric and mass boat parameters on the stability is investigated.

Dynamics and Stability of Boats With Aerodynamic Support

Aerodynamic support is beneficial for achieving very high speeds of marine transportation. Wing-in-ground vehicles, power-augmented ram platforms, and ultrafast planing multihulls are examples of marine craft with air assistance. The main technical problems in the development and application of these concepts for marine transportation are to ensure motion stability and to provide adequate seaworthiness. In this article, the authors illustrate applications of several mathematical models for various air-supported marine vehicle concepts and discuss their specific stability issues. The aerodynamic submodels are based on nonlinear vortex-lattice methods and on the extreme ground effect theory, whereas unsteady hydrodynamics of planing surfaces are treated with added-mass strip theories. The static and dynamic stability in the vicinity of equilibrium states can be analyzed by linearized approaches. However, motions in transient regimes and unsteady environments require implementation of nonlinear and fully unsteady modeling methods.

Fluid Mechanics and Heat Transfer in a Channel with Spherical and Oval Dimples

Vortex mechanism of heat transfer enhancement in a narrow channel with dimples has been investigated numerically using unsteady Reynolds averaged Navier Stokes equations (URANS SST and SAS) and Large Eddy Simulations (LES). The flow separation results in a formation of vortex structures which significantly enhance the heat transfer on dimpled surfaces conducted by a small increase of the pressure loss. The vortex structures and the flow are sufficiently unsteady. The vortex structure inside of the dimple changes steadily its orientation causing the long period oscillations with opposite-of-phase motion. The heat transfer enhancement is caused mostly by the amplification of convection. The effect of the wetted area increase is sufficiently smaller.

Numerical Modeling and Physical Simulation of Vortex Heat Transfer Enhancement Mechanisms Over Dimpled Reliefs

The paper presents a comprehensive analysis of conditions for numerical simulation and physical modeling of convective heat transfer in the vicinity of dimpled surface relief. Contradictory results, unreasonable assumptions, and non-justified conclusions are marked. Based on the analysis of physical experiments the correlation between the predictions and measured data is discussed. Detailed numerical study of turbulent air flow and heat transfer in the narrow channel with three types of dimples (spherical, conic and oval) was carried out. Various mathematical and discrete models, including, those based on solving Reynolds-averaged Navier-Stokes equations (RANS/URANS-SST), and also adaptive scale models (SAS-SST) are compared. The influence of flow parameters (Reynolds number) and geometric sizes (dimple diameter, depth, radius of rounding off of an edge, channel width and height) on local and integral characteristics of flow and heat transfer (total heat output and hydraulic losses) is determined. Special attention is given to reorganizing vortex structures and flow regime (with periodic fluctuations) with increasing relative dimple depth and Reynolds number. For the first time the influence of the scale factor of a constant cross-section channel is detailed. Thermal-hydraulic characteristics of various dimpled reliefs are compared, and the advantage of an oval dimple over a spherical one is shown.Copyright

Investigations of the Safety of Flight of WIG craft

Abstract The paper presents motion simulations in time domain of a WIG craft with a Lippisch configuration under wind and wave perturbations. The aerodynamic characteristics were obtained using the vortex lattice method. The motion is considered in the longitudinal plane. A novel approach is proposed to generate artificial wind turbulence with prescribed kinetic energy and spectra. The wave surface is modeled by a plane performing linear and angular oscillations. Motion simulations were performed to show the limitations of flight safety analysis based on the classic stability theory. Simulation of the take-off motion was carried out to determine the conditions for safe transition from the skimming to flare mode. It was shown that the application of the flight control is necessary for safe flight in the proximity of the ground.

Study of unsteady loadings on the propeller under steady drift and yaw motion using URANS, hybrid (URANS-LES) and LES methods

In this paper, results of computations of unsteady wake and unsteady loadings on marine propellers behind KVLCC2 tanker under different drift angles and yaw rates are presented and analysed. Hybrid unsteady Reynolds averaged equations-large eddy simulations (URANS-LES) presented in [Kornev, N., Taranov, A., Shchukin, E. and Kleinsorge, L. 2011. Development of hybrid URANS-LES methods for flow simulation in the ship stern area. Ocean Engineering, 38, pp.1831–8], hybrid IDDES, k-ω SST URANS and pure LES DMM models are utilised. In the first step, the vortex structures, fluctuations of velocity fields in the nominal wake are analysed behind the bare hull. In the second step, the arrangement containing both hull and rotating propeller is computed with consideration of all interaction effects at different drift angles and yaw rate. It was shown that unsteady loadings on propeller increase at non-zero drift angle and yaw rate.

Simulation of the Dynamics of an Autonomously Acting Small Catamaran for Search and Rescue Process

Abstract Operations of search and rescue are technically very complicated and cause a potential risk for the rescue team. Therefore a new, autonomously acting rescue system is now being under development. Two mathematical models are presented to compute the hydrodynamics of small twin-hull water craft during a search and rescue process at different sea states. Using three and six degrees of freedom they are capable of simulating the navigation of the controlled rescue boat from the parent ship to the person overboard. 3DOF model is validated by comparison with SIMMAN workshop data and results obtained from 6DOF model. Also a study is performed to evaluate the influence of boat parameters on the manoeuvrability.