Turbulence model study for aerodynamic analysis of the leading edge tubercle wing for low Reynolds number flows.

A turbulence model study was performed to analyze the flow around the Tubercle Leading Edge (TLE) wing. Five turbulence models were selected to evaluate aerodynamic force coefficients and flow mechanism by comparing with existing literature results. The selected models are realizable k-ε, k-ω Shear Stress Transport (SST), ( γ - R e θ ) SST model, Transition k-k l -ω model and Stress- ω Reynolds Stress Model (RSM). For that purpose, the TLE wing model was developed by using the NACA0021 airfoil profile. The wing model is designed with tubercle wavelength of 0.11c and amplitude of 0.03c. Numerical simulation was performed at chord-based Reynolds number of Rec = 120,000. The Computational Fluid Dynamic (CFD) simulation reveals that among the selected turbulence models, Stress- ω RSM estimated aerodynamic forces (i.e. lift and drag) coefficients closest to that of the experimental values followed by realizable k-ε, ( γ - R e θ ) SST model, k-ω SST model and k-k l -ω model. However, at a higher angle of attacks i.e. at 16° & 20° k-ω SST model predicted closest drag and lift coefficient to that of the experimental values. Additionally, the critical observation of pressure contour confirmed that at the lower angle of attack Stress- ω RSM predicted strong Leading Edge (LE) suction followed by realizable k-ε, ( γ - R e θ )SST model, k-ω SST model and k-k l -ω model. Thus, the superiority of Stress- ω RSM in predicting the aerodynamic force coefficients is shown by the flow behavior. In addition to this pressure contours also confirmed that k-k l -ω model failed to predict tubercled wing aerodynamic performance. At higher angles of attacks k-ω SST model estimated aerodynamic force coefficients closest to that of the experimental values, thus k-ω SST model is used at 16° & 20° AoAs. The observed streamline behavior for different turbulence models showed that the Stress- ω RSM model and k-k l -ω model failed to model flow behavior at higher AoAs, whereas k-ω SST model is a better approach to model separated flows that experience strong flow recirculation zone.

Prospects of natural gas consumption in Pakistan: based on the LMDI-STIRPAT PLSR framework.

The natural gas (NG) forms the sizeable portion of the primary energy consumption in Pakistan. However, its depleting domestic reserves and increasing demand is challenging to balance the supply-demand in the country. This paper investigates the relationship between NG consumption and driving factors using LMDI-STIRPAT PLSR framework. It is learned that fossil energy structure and per capita gross domestic product (GDP) are most influencing factors on NG consumption, followed by non-clean energy structure, energy intensity, and population. The factors were further modelled to forecast the future values of NG consumption for various scenarios. It is found that NG consumption would be 42.107 MTOE under the high development scenario which would be twice the baseline scenario. It is projected that indigenous NG production will fall from 4 to 2 billion cubic feet/day and demand will increase by 1.5 billion cubic feet/day. Therefore, an optimized strategy is required for a long-term solution to cater this increasing supply-demand.

The impacts of conventional energies on environmental degradation: does Pakistan's economic and environmental model follow the Kuznets curve?

This paper investigates the long-run dynamic association of carbon dioxide emissions and economic progress using the environmental Kuznets curve (EKC) hypothesis for Pakistan from 1972 to 2019. The other variables used along with the above indicators are urbanization, financial development, manufacturing, oil and gas energy consumption, and trade openness. The ARDL bounds testing methodology has been used and the results of the bound testing showed that a 1% increase in economic growth and financial development would increase CO2 emissions in the country by 4.277 and 0.0787%, respectively. Urbanization and manufacturing would increase CO2 emissions by 0.648 and 0.171%, respectively. Oil and gas energy consumption would also increase CO2 emissions by 0.130 and 0.1935%, respectively. Trade openness is the only factor found in the study which decreases emissions in the country in the long run by -0.087%. Besides, findings confirm the EKC hypothesis with the reversed U-shaped relation for per capita CO2 emissions and economic progress. However, the threshold point of the economy is approximately $2735.19 per capita, where economic progress can mitigate the impact of pollution lies beyond the study period, and GDP growth still increases emissions of the country and degrades the environment of Pakistan, as it is not yet reached at the turning level of the economy. As a result, GDP growth is still harming the economy of Pakistan as it has not yet reached the turning point of the economy.

Effect of Polyethylene Glycol and Activated Carbon Macroparticles on Thermal Conductivity of Paraffin Wax for Thermal Storage Applications.

Low thermal conductivity is the major obstacle for the wide range utilization of phase change materials (PCMs), especially organic PCMs, for most practical applications in thermal engineering. This study investigates the potential of enhancing the charging and discharging rates of organic PCM (RT44HC) by introducing polyethylene glycol (PEG) and activated carbon macroparticles (ACMPs). Different concentrations of PEG and ACMPs ranging from 0.3 wt% to 2 wt% were tested separately. The optimized concentrations found were used as dual reinforcements to attain the highest possible thermal conductivity. The specimens were tested for a complete charging-discharging cycle using an improvised thermal apparatus. Use of ACMP alone resulted in a minimal reduction in complete charging-discharging time due to the settlement of ACMPs at the bottom after 2-3 heating-cooling cycles. However, the addition of PEG with ACMPs exhibited a reduction in charging-discharging time due to the formation of a stable dispersion. PEG served as a stabilizing agent for ACMPs. The lowest charging-discharging time of 180 min was exhibited by specimens containing 1 wt% PEG and 0.5 wt% ACMPs which is 25% lower compared to bare PCM.