Blar i NTNU Open på forfatter "Ellingsen, Simen Andreas Ådnøy"
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A Framework for Modeling Linear Surface Waves on Shear Currents in Slowly Varying Waters
Li, Yan; Ellingsen, Simen Andreas Ådnøy (Journal article; Peer reviewed, 2019)We present a theoretical and numerical framework—which we dub the direct integration method (DIM)—for simple, efficient, and accurate evaluation of surface wave models allowing presence of a current of arbitrary depth ... -
Airborne Remote Sensing of Upper-Ocean and Surface Properties, Currents and Their Gradients From Meso to Submesoscales
Lenain, Luc; Smeltzer, Benjamin Keeler; Pizzo, Nick; Maria, Freilich; Colosi, Luke; Ellingsen, Simen Andreas Ådnøy; Grare, Laurent; Peyriere, Hugo; Statom, Nick (Journal article; Peer reviewed, 2023)In this work we present a unique set of coincident and collocated high-resolution observations of surface currents and directional properties of surface waves collected from an airborne instrument, the Modular Aerial Sensing ... -
An Improved Method for Determining Near‐Surface Currents From Wave Dispersion Measurements
Smeltzer, Benjamin Keeler; Æsøy, Eirik; Ådnøy, Anna; Ellingsen, Simen Andreas Ådnøy (Journal article; Peer reviewed, 2019)A new inversion method for determining near‐surface shear currents from a measured wave spectrum is introduced. The method is straightforward to implement and starts from the existing state‐of‐the‐art technique of assigning ... -
Current mapping from the wave spectrum
Smeltzer, Benjamin Keeler; Ellingsen, Simen Andreas Ådnøy (Chapter, 2021) -
Design and control of precision drop-on-demand herbicide application in agricultural robotics
Urdal, Frode; Utstumo, Trygve; Vatne, Jan Kåre; Ellingsen, Simen Andreas Ådnøy; Gravdahl, Jan Tommy (Chapter, 2014)Drop-on-demand weed control is a field of research within Precision Agriculture, where the herbicide application is controlled down to individual droplets. This paper focuses on the fluid dynamics and electronics design ... -
Designing vortices in pipe flow with topography-driven Langmuir circulation
Ellingsen, Simen Andreas Ådnøy; Akselsen, Andreas Holm; Chan, Leon (Peer reviewed; Journal article, 2021)We present direct numerical simulation of a mechanism for creating longitudinal vortices in pipe flow, compared with a model theory. By furnishing the pipe wall with a pattern of crossing waves, secondary flow in the form ... -
Dispersion forces in Micromechanics: Casimir and Casimir-Polder forces affected by geometry and non-zero temperature
Ellingsen, Simen Andreas Ådnøy (Doktoravhandlinger ved NTNU, 1503-8181; 2011:29, Doctoral thesis, 2011)The present thesis focuses on several topics within three separate but related branches of the overall field of dispersion forces. The three branches are: temperature corrections to the Casimir force between real materials ... -
The Effect of Horizontal Shear on Extracting Water Currents From Surface Wave Data
Weichert, Stefan; Smeltzer, Benjamin Keeler; Ellingsen, Simen Andreas Ådnøy (Journal article; Peer reviewed, 2024)The dispersive motion of surface waves is now routinely used to remotely measure the currents close beneath the surface of oceans and other natural flows. The current manifests as wavelength-dependent Doppler shifts in the ... -
Effect on Doppler Resonance From a Near-Surface Shear Layer
Smeltzer, Benjamin Keeler; Li, Yan; Ellingsen, Simen Andreas Ådnøy (Chapter, 2017)For waves generated by a wave source which is simultaneously moving and oscillating at a constant frequency ω, a resonance is well known to occur at a particular value τres of the nondimensional frequency τ = ωV/g (V: ... -
Experimental study of surface waves on strongly sheared currents - Laboratory, design, building, testing, and measurements
Æsøy, Eirik (Master thesis, 2017)In this thesis experimental methods to measure shear-dependent wave dispersion is implemented and used to study waves propagating on currents. To achieve such measurements one needs to establish the following measurement ... -
Experimental study of the mutual interactions between waves and tailored turbulence
Smeltzer, Benjamin Keeler; Rømcke, Olav; Hearst, R. Jason; Ellingsen, Simen Andreas Ådnøy (Peer reviewed; Journal article, 2023)When surface waves interact with ambient turbulence, the two affect each other mutually. Turbulent eddies get redirected, intensified and periodically stretched and compressed, while the waves suffer directional scattering. ... -
Getting the ducks in a row
Ellingsen, Simen Andreas Ådnøy (Peer reviewed; Journal article, 2021)Vessels – in the widest sense – travelling on a water surface continuously do work the water surrounding it, causing energy to be radiated in the form of surface waves. The concomitant resistance force, the wave resistance, ... -
The influence of water turbulence on surface deformations and the gas transfer rate across an air–water interface
Bullee, Pim Adriaan; Weichert, Stefan; Nore, Astri; Li, Leon; Ellingsen, Simen Andreas Ådnøy; Hearst, Robert Jason (Journal article; Peer reviewed, 2024)We present experimental results of a study on oxygen transfer rates in a water channel facility with varying turbulence inflow conditions set by an active grid. We compare the change in gas transfer rate with different ... -
Initial Value Problems for Water Waves in the Presence of a Shear Current
Li, Yan; Ellingsen, Simen Andreas Ådnøy (Proceedings of the twenty-fifth International Ocean and Polar Engineering Conference;ISOPE 2015, Chapter; Peer reviewed, 2015)We obtain a general solution for the initial value problems of water waves with a shear current of uniform vorticity beneath the surface in three dimensions. Linearized governing equations and boundary conditions including ... -
Langmuir-type vortices in wall-bounded flows driven by a criss-cross wavy wall topography
Akselsen, Andreas Holm; Ellingsen, Simen Andreas Ådnøy (Peer reviewed; Journal article, 2020)We investigate a mechanism to manipulate wall-bounded flows whereby wave-like undulations of the wall topography drives the creation of bespoke longitudinal vortices. A resonant interaction between the ambient vorticity ... -
Multiple resonances of a moving oscillating surface disturbance on a shear current
Ellingsen, Simen Andreas Ådnøy; Li, Yan (Journal article; Peer reviewed, 2016) -
Numerical analysis of non-linear oscillations of micrometre size fluid droplets
Frøynes, Olav Are (Master thesis, 2014)Nonlinear oscillations of free viscous drops are investigated by solving the full Navier-Stokes equation using the finite element software COMSOL Multiphysics. Oscillations are investigated for droplets released form static ... -
Numerical simulation of circulation in boundary layers over sinusoidally modulated walls
Brostrøm, Andreas (Master thesis, 2020)Skjærstrømninger over sinusoidalt modulerte vegger har vist å produsere roterende strømninger i et fluid i form av sirkulerende cellepar med motsatt roterende retning. Cellenes roterende akse er parallell med strømningsretningen ... -
Numerical study of curved-mesh tailoring of free-surface shear profile
Ludvigsen, Stian Isefjær (Master thesis, 2019)Krummede nettinger blir ofte brukt til å endre hastighetsprofilet i testområdet i eksperimentelle anlegg. De eksisterende uttrykkene som kan brukes til å bestemme formen på nettingen, gitt strømningsforholdene opp- og ... -
Numerical study of surface waves on a shear current - Waves behind a surface obstacle
Kvamme, Ørjan (Master thesis, 2018)This master's thesis has made investigation into waves and currents interaction numerically by the use of an oscillating cylinder as a wave-maker. Three cases were investigated: still water, uniform flow and linear shear ...