Open Access Others

Corrigendum: Effects of Suction and Thermal Radiation on Heat Transfer in a Third Grade Fluid over a Vertical Plate

I. G. Baoku

Physical Science International Journal, Page 1-16
DOI: 10.9734/PSIJ/2016/8964

Aims: An analysis is presented to investigate the effects of suction and thermal radiation on the unsteady convective hydromagnetic flow and heat transfer in a third grade fluid over an infinite vertical plate. The plate is porous to allow for possible wall suction. Viscous dissipation and Joule heating effects are also taking into consideration.

Methodology: The governing time-based coupled partial differential equations, subjected to their boundary conditions, are solved numerically by applying an efficient and unconditionally stable Crank-Nicolson finite difference scheme. Numerical calculations are carried out for different values of dimensionless parameters in the problem.                                       

Results: An analysis of the results obtained establishes that the flow field is appreciably influenced by suction, magnetic interaction and viscoelastic parameters.

Conclusion: An increase in the suction parameter is observed to decrease the fluid velocity. The result also shows that the temperature distribution decreases with an increase in the thermal radiation parameter.

 

Open Access Commentary

Signs of Stability of the Arctic Sea Ice Thickness from Cryosat-2

A. Parker

Physical Science International Journal, Page 1-8
DOI: 10.9734/PSIJ/2016/22017

The signs of stability of the sea ice thickness from the latest Cryosat-2 results for the Arctic sea ice thickness are consistent with the Lower Troposphere Temperatures (LTT) and the sea ice extension results available since 1979. In the longer term, the current Arctic climate is probably at the start a cooling and recovery phase part of the same quasi-60 years’ oscillation that was responsible of most of the warming since the late 1970s. This natural variability is superimposed on a longer-term trend of warming temperatures and shrinking of sea ice that started in the 1800s.

 

Open Access Short communication

Probability Density Function of Scalar Length Scales in Turbulent Flow

Andrei Chorny

Physical Science International Journal, Page 1-6
DOI: 10.9734/PSIJ/2016/22455

In this Brief Communication scalar length-scale and time-scale distributions are proposed to determine by considering the statistics of the scalar field and its gradient. For this purpose, a relationship between the scalar length-scale probability density function and the joint probability density function for the scalar field and its gradient in the form of the integral relation is established.

 

Open Access Original Research Article

Improvement of Cryogenic Space Rocket Engine Ignition: Inert Gas Sweep Effects

Philippe Fauquet-Alekhine

Physical Science International Journal, Page 1-14
DOI: 10.9734/PSIJ/2016/22317

Ignition of cryogenic engines of space launchers is usually preceded by a transient phase during which feeding lines of the combustion chamber are swept by an inert gas. This sweeping flow may be prolonged for several milliseconds while propellants injection begins.

Despite the fact that this transient may generate instabilities influencing the ignition process, related oscillations have not been investigated. Experiments were carried out with nitrogen flowing in a full scale injector of HMB7 engine (equipping Ariane 5 launcher) in thermo-hydrodynamic conditions of similitude with oxygen flow in HM7B (actual oxider propellant of HM7B). Two conditions were investigated: 1) with nitrogen only, 2) with helium gas injected simultaneously with nitrogen during the initial 150 milliseconds. The aim was to characterize the instabilities occurring during a pre-ignition transient of 300 ms and the effect of the inert gas sweep on these instabilities.

Impact force of the jet, density and pressure at injector exit were measured by means of load cell, piezoresistive sensor and resonance cavity respectively. Mass flow was then calculated through momentum equation and slip ratio correlation.

Measurements and analysis showed that the flow was inverted annular flow and mist flow, instabilities were of thermoacoustic oscillation (TAO) type, and led to suggest the thermal effect as the major effect in the production of these oscillations. This also showed that a prolonged sweep of the injector with inert gas had a stabilizing effect on the two-phase flow due to the reduction of wall heat flux and of the inlet subcooling enthalpy. This finding is of great interest also because it shows that TAO are generated in the unit engine much earlier than ignition inside the combustion chamber. Possible coupling between these TAO and those occurring after ignition during combustion (which have different source and with different sustaining factors) might bring interesting knowledge regarding engine ignition process.

 

Open Access Original Research Article

Developing a Fast Affordable Automatic Counting System of CR-39 Solid State Nuclear Track Detectors

M. Alssabbagh, B. Z. Shakhreet

Physical Science International Journal, Page 1-9
DOI: 10.9734/PSIJ/2016/22652

The CR-39 solid state passive nuclear track detector is a popular method to measure charged particle such as alpha and protons and uncharged particles such as neutrons, due to its low cost, robustness, track permanence, and insensitivity to gamma, X-ray, beta and electromagnetic waves.

Traditional methods for processing CR-39 involve manual counting of the damage trails in the detector using an optical microscope: however, such methods are labor intensive and highly operator-dependent.

The main aim of this research is to develop an affordable and fast automatic CR-39 track counting system. A set of CR-39 detectors with dimensions of 1.5 ´ 1.3 cm were exposed to 226Ra with an activity of 122 KBq for different periods of time. A full digital microscope with an LCD monitor of an area of 3.5” which acts as a 10x eyepiece was used to capture the images from the detectors.

Three thresholds (size, Optical Density (OD) and circularity of the tracks) were applied to identify these tracks and facilitate in counting them. The automatic system was then compared to the manual counting method for verification. The P-value was higher than 0.05 (t-test: P-value for 2-tails = 0.99) that showed an insignificant difference between the manual and automatic counting. The system showed a good ability to find and count elliptical tracks using a simple algorithm depending on their circularity values. This system was seen to analyze the tracks effectively, taking less than one minute per detector. The system is almost fully automatic, fast and affordable.

 

Open Access Original Research Article

A Survey of Radiation Levels Associated with Exposure to Power-line in Some Selected Areas in Ibadan Metropolis, Oyo State, Nigeria

Ali Haruna, Olatunbosun Rabiu Oladayo

Physical Science International Journal, Page 1-6
DOI: 10.9734/PSIJ/2016/22828

Measurement of electric field strength, magnetic field strength and power density were carried out using two instruments, electro smog meter (model TES -92) and ELF detection meter (model 480823) at an interval of 2 m starting from the base of the source. The maximum electric field strength, magnetic field strength and power density obtained in this research are 5.09 V/m, 0.2037 A/m and 0.5002 W/m2 respectively. Three of 132 KVA are located at three different communities, Ayede/Jericho, IITA and Ojoo, and three of 11 KVA are also located at three different communities, Odo – Ona, State secretariat and Sango- UI. The maximum electric field strength, magnetic field strength and power density measured as radiated from 132 KVA are 5.09 V/m, 0.0135 A/m and 0.500 W/m2 (Ayede/Jericho), 3.535 V/m, 0.003694 A/m and 0.06874 W/m2 (IITA), 1.3284V/m, 0.00942 A/m and 0.00457 W/m2 (Ojoo) respectively. Also, the maximum electric field strength, magnetic field strength and power density measured as radiated from 11 KVA are 0.0658 V/m, 0.02037 A/m and 0.0006278 (Odo- Ona), 1.619 V/m, 0.00393 A/m and 0.0696 W/m2 (State secretariat), 0.6046 V/m, 0.00225 A/m and 0.00155 W/m2 respectively. These results constitute 0% of the recommended values by the ICNRP. Therefore, peoples living or carrying out other activities along power lines at these sites will not suffer any health hazards due to electromagnetic radiations emanating from the power lines.