Muhammad S. Virk

Effect of Rime Ice Accretion on Aerodynamic Characteristics of Wind Turbine Blade Profiles

A numerical study of rime ice accretion and resultant flow field characteristics of blade profiles for four different fixed speed, stall controlled wind turbines was performed. Analyses were carried out at Reynolds numbers ranging from of 2.5 × 106 to 5.5 × 106, corresponding to the operational wind speeds and angles of attack ranging from −10 degree to + 20 degree. Numerical analyses showed that an increase in blade profile size reduces the dry rime ice accretion at leading edge, both in terms of local mass and ice thickness. A significant change in the flow behaviour and aerodynamic characteristics is observed, when a comparison is made between plain and iced blade profiles. Results showed an increase in both lift and drag coefficients of wind turbine blade profiles with the leading edge ice.

Quantitative Analysis of Accuracy of Voidage Computations in CFD-DEM Simulations

CFD-DEM (Computational Fluid Dynamics — Discrete Element Modelling) is a two-phase flow numerical modelling technique, where the Eulerian method is used for the fluid and the Lagrangian method for the particles. The two phases are coupled by a fluid-particle interaction force (i.e. drag force) which is computed using a correlation. In a two-phase flow, one critical parameter is the voidage (or void fraction), which is defined as the ratio of the volume occupied by the fluid to the total volume. In a CFD-DEM simulation the local voidage is computed by calculating the volume of particles in a given fluid cell. For spherical particles, this computation is difficult when a particle is on the boundary of fluid cells. In this case, it is usual to compute the volume of a particle in a fluid cell approximately. One such approximation divides the volume of a particle into each cell in the same ratio as an equivalent cube of width equal to the particle diameter. Whilst this approach is computationally straight forw...

Dielectric based sensing of atmospheric ice

Atmospheric ice is a naturally occurring mixture with lots of variations. It doesn’t only bind the chemistry of water, but also its physics. The variations of this complex mixture are directly associated with the surrounding dynamics. In this paper we are mainly concerned about the variations in the electrical properties of atmospheric ice due to variation in the surrounding temperature, conductivities, volumetric contents and relaxation time. All these variations are conveniently measured using the permittivity/dielectric sensing principles. Also these calculations can later be utilized to formulate the atmospheric ice type, icing rate and ice thickness.

Atmospheric Ice Loading and Its Impact on Natural Frequencies of Wind Turbines

Wind energy is a promising way in the middle of growing demand for clean energy in high north, where atmospheric icing is a hazard for safe operations of wind turbines. In this research work, the vibrational effects due to atmospheric ice accretion on a multi megawatt large wind turbine are numerically investigated using a finite element based approach. Three different icing scenarios were addressed and accreted on-blade ice mass was calculated analytically based upon ISO 95214 standards. Special attentions are given to the first natural frequency of the wind turbine blade and its interaction when the exciting frequency approaches the natural frequency of the wind turbine tower. Results show variations of natural frequencies due to different accreted icing loads scenarios, which may have different implications to the integrity of the structure.

Numerical analysis of fluid mixing in T-Type micro mixer

Micro fluidic system holds promise for many novel applications within chemistry, biology and medicine. Mixing at micro scale with in a reasonable time period and length scale is important, but despite a large number of studied, no systematic study has been carried out so far to understand the effect of flow mechanism and geometry on micro fluidic mixing. Present study analyze the mixing of low Reynolds number (< 25) fluids in T-type passive micro mixer under various geometric and flow conditions to analyze their relative effects on mixing by diffusion and dispersion. CFD base steady state numerical simulations were carried out using finite element method. Results from this study shows that required mixing length increases with the increase of Reynolds number and mixing channel width, while there is a considerable decrease in mixing length with the increase of diffusion coefficient and mixing channel aspect ratio.

Relation Between Angle of Attack and Atmospheric Ice Accretion on Large Wind Turbine's Blade

A numerical study of wind turbine blade profiles angle of attack variation on atmospheric ice accretion near the blade tip section was performed. Three dimensional computational fluid dynamics (CFD) based numerical analyses were carried out using NACA 64618 blade profile at five different angles of attack ranging from −5 to +7.5 degrees. Based upon the flow field calculations and the super cooled water droplet collision efficiency, the rate and shape of accreted ice was simulated for both rime and glaze ice conditions. The results show that atmospheric icing is less severe at lower angles of attack, both in terms of local ice mass and relative ice thickness.

A Review of the Effects of Ice Accretion on the Structural Behavior of Wind Turbines

Icing of wind turbines happens occasionally at different latitudes and locations in the world and consequently affects the wind turbine fatigue loads. Large ice accretion may cause wind turbine vibration due to uneven ice shedding, which could lead to structural failures in addition to hazardous issues accompanied with ice being shed off wind turbine blades. In this paper, a review study of the effects of ice accretion on the structural behavior of the wind turbines is presented.

Numerical Study of Atmospheric Icing on Non Rotating Circular Cylinders in Tandem Arrangement

Numerical study of atmospheric ice accretion on two non-rotating circular cylinders in tandem arrangement was carried out at different operating and geometric conditions. To validate the numerical model, initially the results of ice accretion on single circular cylinder were compared with the experimental data obtained from CIGELE atmospheric icing research wind tunnel (CAIRWT) [1, 2]. A good agreement was found between experimental and numerical results. Numerical analyses of ice accretion on two circular cylinders in tandem arrangement showed that accreted ice loads decreases with the increase in distance between the cylinders and also affects the rate and shape of ice accretion. Parametric study at different droplet sizes and temperatures showed a significant change in ice accretion. This research work provides a useful base for better understanding and further investigation of atmospheric ice accretion on circular overhead power network cables in tandem arrangement, installed in the cold regions.

Numerical Study of Atmospheric Ice Accretion on Various Geometric Cross-sections

This paper describes the numerical study of atmospheric ice accretion on four different geometric cross sections, circular, parabola, triangle and cube. Most structures are the combination of these four basic geometric cross sections. Understanding of the atmospheric ice accretion physics on these will provide a base for further analyses of ice accretion and its effects on complex structures. CFD based numerical analyses are carried out in this research work to understand the rate and shape of atmospheric ice growth on these cross sections. For constant wind speed and atmospheric temperature, the ice growth is simulated as function of time, where more ice accretion is found on cube as compared to three other cross sections. Parametric study to understand the effect of iced surface roughness showed a significant difference in ice growth, when compared with the case, where no surface roughness was assumed on the cross sections.This paper describes the numerical study of atmospheric ice accretion on four different geometric cross sections, circular, parabola, triangle and cube. Most structures are the combination of these four basic geometric cross sections. Understanding of the atmospheric ice accretion physics on these will provide a base for further analyses of ice accretion and its effects on complex structures. CFD based numerical analyses are carried out in this research work to understand the rate and shape of atmospheric ice growth on these cross sections. For constant wind speed and atmospheric temperature, the ice growth is simulated as function of time, where more ice accretion is found on cube as compared to three other cross sections. Parametric study to understand the effect of iced surface roughness showed a significant difference in ice growth, when compared with the case, where no surface roughness was assumed on the cross sections.

Numerical study of atmospheric ice accretion on rotating geometric cross sections with fins

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