The evolution of a separated boundary layer over a model airfoil with semicircular leading-edge has been illustrated for angles of attack (α) varying from −3 deg to 10 deg, where the Reynolds number (Rec) based on chord is 1.6 × 105 and the inlet freestream turbulence (fst) being 1.2%. The features of boundary layer are described through measurements of velocity and surface pressure besides the flow visualization using a planar particle image velocimetry (PIV). Freestream perturbations are amplified because of enhanced receptivity of the separated boundary layer resulting in pockets of disturbances, which then propagate downstream attributing to random fluctuations near the reattachment. The separation and reattachment locations including the onset and end of transition are identified for changing α. The reattachment point changes from 18.8% to 47.7% of chord with the onset of separation at almost 7%, whereas the onset of transition moves upstream from 13.2% to 9% with increasing α. The bubble bursting occurs at α = 10 deg. The transition in the separated boundary layer occurs through Kelvin–Helmholtz (K–H) instability for α = 0 deg and 3 deg, whereas the K–H mechanism is bypassed for higher α with significant viscous effect.

The behaviour of a separated shear layer past a semi-circular leading edge flat plate, its transition and reattachment downstream to separation are investigated for different imposed pressure gradients. The experiments are carried out in a blowing tunnel for a Reynolds number of 2.44×105 (based on chord and free-stream velocity). The mean flow characteristics and the instantaneous vector field are documented using a two-component LDA and a planar PIV, whereas, surface pressures are measured with Electronically scanned pressure (ESP). The onset of separation occurs near the blend point for all values of β (flap angle deflection), however, a considerable shift is noticed in the point of reattachment. The dimensions of the separation bubble is highly susceptible to β and plays an important role in the activity of the outer shear layer. Instantaneous results from PIV show a significant unsteadiness in the shear layer at about 30% of the bubble length, which is further amplified in the second half of the bubble leading to three-dimensional motions. The reverse flow velocity is higher for a favourable pressure gradient (β = +30°) and is found to be 21% of the free stream velocity. The Reynolds number calculated based on ll (laminar shear layer length), falls in the range of 0.9×104 to 1.4×104. The numerical values concerning the criterion for separation and reattachment agree well with the available literature.

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The hydrogenolysis of dilute glycerol solution to 1,2-propanediol was studied in the presence of heterogeneous catalyst (FeCoL/Raney Nickel) having a heterodinuclear FeCo macrocyclic complex ionically bonded to Raney Nickel. Studies on the stability of the complex bonded to the support were carried out at different temperature as well as the effect of solvent to confirm that it was stable up to 600 • C and 100 h of refluxing. In the hydrogenolysis of glycerol, the temperature has been varied from 165 to 220 • C with an initial hydrogen pressure 0.35 MPa and the conversion increases from 1% to 36% with no gases evolving in this temperature range. The major product is 1,2-propanediol which is formed with 80% selectivity. The initial water content (20-60%) in the feed was also varied and it was found that the conversion and yield of 1,2-propanediol increases when the water content increases. Based on literature, a kinetic model was proposed and optimal rate constants determined using Genetic Algorithm (GA).On aétudié l'hydrogénolyse d'une solution diluée de glycérol solution en 1,2-propanediol, en présence d'un catalyseur hétérogène (FeCoL/nickel de Raney) ayant un complexe macrocyclique hétérodinucléaire de FeCo ioniquement lié au nickel de Raney. Desétudes sur la stabilité du complexe lié au soutien ontété effectuéesà différentes températures et on aétudié aussi l'effet du solvant pour confirmer qu'ilétait stable jusqu'à 600 • C et 100 h de reflux. Dans l'hydrogénolyse du glycérol, la température variait de 165à 220 • C avec une pression initiale d'hydrogène de 0,35 MPa et la conversion augmente de 1%à to 36% sansévolution des gaz dans cet intervalle de température. Le produit majeur est le 1,2-propanediol, lequel est formé avec une sélectivité de 80%. Le contenu d'eau initial (20%à 60%) dans l'alimentation variaitégalement et on a conclu que la conversion et le rendement de 1,2-propanediol augmentait avec les augmentations de contenu d'eau. En se basant sur la littérature, un modèle cinétique aété proposé et des constantes de taux optimal ontété déterminées en utilisant un algorithme génétique.

Shear layer development over a thick flat plate with a semi-circular leading edge is investigated for a range of angles of attack under different pressure gradients for a Reynolds number of 2.44×10 5 (based on chord and free-stream velocity). The characteristics of the separated shear layer are very well documented through a combination of surface pressure measurement and smoke flow visualization. The instability of the separated layer occurs because of enhanced receptivity of perturbations leading to the development of significant unsteadiness and three-dimensional motions in the second-half of the bubble. The onset of separation, transition and the point of reattachment are identified for varying angles of attack and pressure gradients imposed by tail flap deflections. The data concerning bubble length, laminar portion and reattachment points agree well with the literature.