Sharif Digital Repository

In the current study, experimental tests are conducted to evaluate the hydrodynamic characteristics and the bottom wetted surfaces of the planing hulls equipped by one transverse step. For this purpose, total resistance, dynamic trim angle, dynamic sinkage, reattachment lengths of the separated flow and forebody and aftbody wetted areas are quantitatively measured at different geometrical parameters of the step and hull velocities. Moreover, the bottom wetted surfaces are qualitatively investigated by analyzing the underwater photographs. Our experimental results are also compared by archival data with good accordance. Based on our experimental observations, dynamic trim angle and dynamic... 

To obtain potentially applicable microorganisms to an effective in situ microbial enhanced oil recovery operation, bacteria that were compatible with the harsh conditions of a petroleum reservoir were isolated from a crude oil sample. The application of an oil spreading technique showed that all of the isolates were capable of producing biosurfactants from both the glucose and crude oil as carbon sources. The secreted biosurfactants could at least reduce the surface tension 20 mN/m and for one of the isolates; the surface tension value dropped below 40 mN/m. In addition, the contact angle measurements revealed that the produced biosurfactants could effectively alter the wettability of the... 

The dynamics and stability of rotating circular cylindrical shells partially filled with ideal liquid is analyzed. The structural dynamics of the shell is modeled by using the first-order shear deformable shell theory and the flow inside the cylinder is simulated by a quasi 2D model based on the NavierStokes equations for ideal liquid. The fluid and structural models are combined using the nonpenetration condition of the flow on the wetted surface of the cylinder and the fluid pressure on the flexible shell. The obtained fluidstructure model is employed for the determination of the stable regions of the spinning frequency of the cylinder. A series of case studies are performed on the... 

To obtain metallic nanofingers applicable in surface acoustic wave (SAW) sensors, a mechano-chemical atomic force microscope (AFM) nanolithography on a metallic thin film (50 nm in thickness)/piezoelectric substrate covered by a spin-coated polymeric mask layer (50-60 nm in thickness) was implemented. The effective shape of cross-section of the before and after etching grooves have been determined by using the AFM tip deconvolution surface analysis, structure factor, and power spectral density analyses. The wet-etching process improved the shape and aspect ratio (height/width) of the grooves and also smoothed the surface within them. We have shown that the relaxed surface tension of the... 

Low salinity water flooding (LSWF) has the potential to enhance the oil recovery by affecting the fluid-fluid and rock-fluid interactions. Therefore, a systematic investigation on the effect of initial wetting state (water-wet or oil-wet) of pure calcite is conducted to study the importance of these interactions on the effectiveness of LSWF. In the case of initially water-wet cores, more oil recovery efficiency is observed for more saline water cases. To shed light on the possible involved mechanisms, dynamic IFT, dynamic contact angle (CA), oil/brine and rock/brine surfaces zeta potentials, and effluent pH are measured. It is shown that the short-term effect of IFT reduction and long-term... 

It is well known that the oil recovery is affected by wettability of porous medium; however, the role of nanoparticles on wettability alteration of medium surfaces has remained a topic of debate in the literature. Furthermore, there is a little information of the way dispersed silica nanoparticles affect the oil recovery efficiency during polymer flooding, especially, when heavy oil is used. In this study, a series of injection experiments were performed in a five-spot glass micromodel after saturation with the heavy oil. Polyacrylamide solution and dispersed silica nanoparticles in polyacrylamide (DSNP) solution were used as injected fluids. The oil recovery as well as fluid distribution in... 

A bacterial strain was isolated and cultured from the oil excavation areas in tropical zone in southern Iran. It was affiliated with Pseudomonas. The biochemical characteristics and partial sequenced 16S rRNA gene of isolate, MR01, was identical to those of cultured representatives of the species Pseudomonas aeruginosa. This bacterium was able to produce a type of biosurfactant with excessive foam-forming properties. Compositional analysis revealed that the extracted biosurfactant was composed of high percentages lipid (∼65%, w/w) and carbohydrate (∼30%, w/w) in addition to a minor fraction of protein (∼4%, w/w). The best production of 2.1 g/l was obtained when the cells were grown on...