
John Grue- University of Oslo
John Grue
- University of Oslo
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43
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Publications (43)
Free wave generation due to a ship or storm moving past a shallow, great depth change of the water, is measured on the shore (coast), modeled and compared. The free waves are generated at the depth change where the forced wave and velocity field attached to the moving pressure system adjust to the new depth. The wavenumber is a factor 1/12 smaller...
Runup on a slender cylindrical column exposed to long, steep waves, at finite and great depth is quantified by high speed camera technique in wave channel. Ratio between water depth (h) and cylinder diameter (D) is h/D=10,4.16 and 2.5. Breaking and non-breaking wave events are made by focusing technique. The trough-to-trough period (TTT), crest hei...
The internal wave (dead water) resistance on the Polar ship FRAM is obtained by two methods. The first is empirical, based on the original observations (Nansen, F.: Farthest North, Westminster: Archibald Constable and Company, 2 Whitehall Gardens, 1897. Vol. 1). The second is a strongly nonlinear interfacial method in three dimensions. The intersec...
Very long waves are generated when a ship moves across an appreciable depth change $\unicode[STIX]{x0394}h$ comparable to the average and relatively shallow water depth $h$ at the location, with $\unicode[STIX]{x0394}h/h\simeq 1$ . The phenomenon is new and the waves were recently observed in the Oslofjord in Norway. The 0.5–1 km long waves, extend...
Supercritical ship internal wave wakes with $Fr=U/c_{0}\sim 4{-}12$ (where $U$ is the ship speed and $c_{0}$ is the linear internal long-wave speed) are calculated by a strongly nonlinear two-layer model in three dimensions, accounting for the complex ship geometry, and compared with field measurements. The degree of nonlinearity, defined by the sh...
A nonlinear calculation procedure for obtaining the wave kinematics from elevation measurements from field data is outlined in detail. A horizontal current is accounted for. The numerical calculations from the field data are compared to the kinematics of random waves obtained in laboratory measurements.
The dead water resistance F1 = 1 2Cdw ρSU2 (ρ fluid density, U ship speed, S wetted body surface, Cdw resistance coefficient) on a ship moving at subcritical speed along the upper layer of a two-layer fluid is calculated by a strongly nonlinear method assuming potential flow in each layer. The ship dimensions correspond to those of the Polar ship F...
We present an overview of the continuous and discontinuous Galerkin finite element methods (CG-FEM, DG-FEM) for numerical solution of the transport equation and show how the Navier-Stokes equations can be solved with CG-FEM in both a coupled and segregated manner. We show convergence of the implemented Navier-Stokes solvers for single-phase flows o...
A three-dimensional two-layer, fully dispersive and strongly nonlinear interfacial wave model, including the interaction with a time-varying bottom topography, is developed. The method is based on a set of integral equations. The source and dipole terms are developed in series expansions in the vertical excursions of the interface and bottom topogr...
Interfacial gravity driven motion of a two-fluid system bounded above and below by rigid lids, is studied. The interfacial motion is three-dimensional, fully nonlinear and fully dispersive. By the method of successive approximations, various approximations of the method are derived, where the truncated versions are computationally fast, still being...
Honji instability and ringing of offshore structrures are two different phenomena. Honji instability occurs at a circular cylinder in transverse periodic finite motion in a water tank. It is superposed on the streaming flow induced by the cylinder's boundary layer. Its oscillation period is half of the period of the cylinder oscillation. Finite vol...
We review recent laboratory studies and numerical calculations of breaking and non-breaking internal solitary waves of very large amplitude, the status of nonlinear computations and stability calculations, with comparison to field observations, both in the upper ocean and close to the bottom. Internal run-up at the continental slope, strong bottom...
Accurate representations of the surface potential and the orbital velocity of nonlinear water waves are obtained, given the
spatial wave-elevation field and its time derivative along two-dimensional sections of the ocean surface. The effect of a
horizontal current is accounted for. The method is three-dimensional. The kernel of an integral equation...
A data base of the recent Gulf of Tehuantepec experiment, of measured elevation of ocean surface waves in strong wind conditions, over swaths that are 6 km long by 200 m wide, is used as input for computation of the orbital velocity of the waves. Linear, quadratic and cubic approximations are compared to computations using a fully nonlinear-dispers...
Deformation of the Indian Ocean tsunami moving into the shallow Strait of Malacca and formation of undular bores and solitary waves in the strait are simulated in a model study using the fully nonlinear dispersive method (FNDM) and the Korteweg-deVries (KdV) equation. Two different versions of the incoming wave are studied where the waveshape is th...
The nonlinear dynamics of three-dimensional instabilities of uniform gravity-wave trains evolving to crescent wave patterns is investigated numerically. A new mechanism of generation of oscillating horseshoe patterns is proposed and a detailed discussion on their occurrence in a water wave tank is given. It is suggested that these patterns are more...
A numerical study of the instabilities of Stokes waves on finite depth has been carried out using an efficient fully nonlinear method [D. Clamond and J. Grue, ``A fast method for fully nonlinear water-wave computations,'' J. Fluid Mech. 447, 337 (2001)]. First, attention is given to five-wave instabilities with k0h=O(1), k0 being the wavenumber and...
An efficient numerical scheme for simulations of fully nonlinear non-breaking surface water waves in 3D is presented. The water depth is either shallow, finite or infinite. The method is based on a fast, rapidly converging, iterative algorithm to compute the Dirichlet to Neumann operator. This is evaluated by expanding the operator as a sum of glob...
Introduction Vortex Induced Vibrations (VIV) phenomena cause problems in many areas related to oshore engineering. Large structures such as a Spar platform may experience VIV. Most often this problem area is related to risers and pipelines in free spans, as well as with vibrations of tubular members in are booms. The important of streamwise vibrati...
Fully nonlinear computations of solitary waves with a thick or thin pycnocline are investigated and compared with experiments and interfacial model predictions. The effect of a stratified upper layer on wave induced velocities and potential breaking of the waves are investigated. The wave induced vorticity within the pycnocline and in the surface l...
In this paper we use an industrial Navier–Stokes (NS) solver to model high amplitude internal waves. The model simulates a fluid with a shallow upper layer with linear stratification and a deep lower layer with constant density, relevant to conditions in the ocean at several locations. Waves are generated by trapping a volume of light water behind...
The role of the time-averaged second order potential in the drift-wave damping problem is studied. A floating body moving with slow velocities in the three dimensional modes of motion while responding to incoming monochromatic wave with amplitude A is considered. The potential theory is applied to describe the motion of the fluid which is assumed t...
Waves and Nonlinear Processes in Hydrodynamics contains thirty-one papers by international experts in hydrodynamics based on talks at a symposium held in honour of Professor Enok Palm on his 70th birthday. The volume begins with two review papers on the history of hydrodynamic research at the University of Oslo and on engineering applications of hy...
In December 1994 Professor Enok Palm celebrated his 70th birthday and retired after more than forty years of service at the University of Oslo. In view of his outstanding achievements as teacher and scientist a symposium entitled "Waves and Nonlinear Processes in Hydrodynamics" was held in his honour from the 17th to the 19th November 1994 in the l...
Wave drift damping and low-frequency oscillations of a moored elliptic cylinder is examined. The cylinder is restricted to move along a horizontal frictionless constraint. The moorings are simulated by slack linear springs. The fluid layer is infinitely deep and the motion is two-dimensional. The fluid flow around the body and the forces acting upo...
The effect of a uniform current on slowly varying forces is examined. The model is two-dimensionaland the body is either a restrained or a moored submerged circular or elliptic cylinder. Newman's approximation is applied to approximate the slowly varying forces. The spectral density function for the force is studied for various current speeds. It i...
The time-periodic pressure loading, added mass, damping, and exciting forces on a horizontal submerged circular cylinder in a current are examined. The fluid layer is infinitely deep and the motion is two-dimensional. The boundary-value problem is solved by applying a source distribution along the contour of the body. The forces become finite for τ...
Fully nonlinear simulations of freak waves in three-dimension are investigated by a rapid numerical procedure. The method solves the Laplace equation by using the Green function method, that is reformulated in a quickly computable way. This method has already been proved useful for two-dimensional problems. We investigate the three-dimensional effe...
The nonlinear Schrodinger-like equations (NLS, Dysthe, etc.) are widely used models for investigating the evolution of surface gravity waves with narrow-banded spectra. Such models have recently been used in attempts for describing and understanding freak wave formations. We numerically compare these simplified models with a fully nonlinear one. In...
Internal waves are generated many places in the world's oceans. The waves induce rather strong currents that have implications to offshore installations. It is particu- larly the loads and motions induced by the currents that represent the concern, such as, vortex induced vibrations of long cables, pipelines, moorings or risers. Other con- cerns re...
Interaction between steep water waves and fixed or moving bodies at the surface of the ocean represents continued interest from theoretical, experimental and practical point of view. Linear and weakly nonlinear wave-body interaction theories are well developed and implemented in computer codes for industrial use. The next step for the offshore indu...
Forces on floating structures with a small forward speed oscillating in incoming waves are studied mathematically. Coupling between the oscillatory wave field and the steady flow around the body is accounted for. Friction and separation effects are disregarded, and the fluid flow is modelled by potential theory. The boundary value problem for the v...