arXiv subjects

Sverre Gullikstad Johnsen

Publications and source records attributed to Sverre Gullikstad Johnsen.

5 recordsLinked to original sources

arXiv2022

A Review of Experimental Solubilities and a General Correlation between the Temperature-Dependent Solubility and Solute and Solvent Molar Masses for Binary n-Alkane Mixtures

The solubility of a "heavy" alkane (solute) in a "light" alkane (solvent) is generally temperature dependent. Moreover, it is determined by the molar masses of the solute and solvent. In the current paper, published solubility data for binary normal-alkane mixtures is reviewed (solid-liquid equilibrium). A total of 43 unique solute-solvent data-sets, obtained from a total of 24 published experimental studies, are collected and presented in a systematic manner. Based on thermodynamic considerations and the experimental data, it is demonstrated that there is a log-linear relationship between the solubility and the temperature in the dilute range. Linear regression is employed to 1) obtain data-set-specific solubility-temperature best-fit parameters and 2) obtain a general correlation between the solubility and the solvent and solute molar masses and the temperature. Finally, it is demonstrated that the developed correlation carries predictive power even for multi-component mixtures by utilizing solvent and solute average molar masses.

physics.chem-ph↗

arXiv2018

On the Rheology of Newtonian Single-Phase Multicomponent Mixtures

In the turbulent boundary layer of multicomponent fluid mixtures, the species-specific mass flux is determined by the combination of turbulent-diffusiophoretic diffusion and diffusion due to gradients in supplementary fields (e.g. temperature). For inert mixtures, a balance must exist between all the diffusive transport mechanisms so that the net diffusive mass flux normal to the wall is zero everywhere. This may require non-constant composition profiles. Implications are discussed, and mathematical modelling is employed to demonstrate how this may affect fluid property profiles, wall heat flux, and wall shear stress in a Newtonian ternary gas mixture ($H_2 + N_2 + CO_2$) subject to a temperature gradient.

physics.flu-dyn↗

arXiv2017

A wall-function approach for direct precipitation/crystallization fouling in cfd modelling

The main objective of this paper is to present a generic modelling framework, for the diffusive mass transport through the turbulent, reactive boundary layer of multi-component fluid mixtures that precipitate on the wall. The modelling is based on Maxwell-Stefan diffusion in multi-component mixtures, the relaxation to chemical equilibrium model, and the single-phase Navier-Stokes equations. Final-ly, turbulence is introduced by Reynolds-averaging. The governing equations are simplified in accordance with common assumptions of computational fluid dynamics (CFD), and based on the assumption that the over-all bulk flow is parallel to the wall, 1-dimensional equations for the species and heat transport perpendicular to the wall have been formulated. The equations are solved on a fine grid in order to fully resolve the boundary layer, and the effect of allowing/disallowing deposition and chemical reactions was investigated for a simplified test-case (4-component ideal mixture of perfect gasses capable of chemical reaction and sublimation fouling). The developed framework can be employed as a sub-grid model for direct precipitation/crystallization/solidifica-tion fouling in coarse grid CFD models.

physics.flu-dyn↗

arXiv2017

CFD simulations of turbulent flow in the human upper airways

In this paper, investigations are conducted using Reynolds-averaged Navier-Stokes (RANS) turbulence models to investigate the importance of turbulence modelling for nasal inspiration at a constant flow rate of 250 ml/s. Four different, standard turbulence models are tested in a model geometry based on pre-operative CT images of a selected obstructive sleep-apnea syndrome (OSAS) patient. The results show only minor differences between them. Furthermore, the turbulence models do not give significantly different results than a laminar flow model. Thus, the main conclusion is that effects of turbulence are insignificant in CFD modelling of the airflow in the pre-operative model of the upper airways of the chosen patient.

physics.med-ph↗

arXiv2017

Patient specific numerical simulation of flow in the human upper airways for assessing the effect of nasal surgery

The study is looking into the potential of using computational fluid dynamics (CFD) as a tool for predicting the outcome of surgery for alleviation of obstructive sleep apnea syndrome (OSAS). From pre- and post-operative computed tomography (CT) of an OSAS patient, the pre- and post-operative geometries of the patient's upper airways were generated. CFD simulations of laminar flow in the patient's upper airway show that after nasal surgery the mass flow is more evenly distributed between the two nasal cavities and the pressure drop over the nasal cavity has increased. The pressure change is contrary to clinical measurements that the CFD results have been compared with, and this is most likely related to the earlier steps of modelling - CT acquisition and geometry retrieval.

physics.med-ph↗