NUMERICAL PREDICTION OF SCALE EFFECTS ON THE PROPULSION PERFORMANCE OF JOUBERT BB2 SUBMARINE

The motivation of this study is to present the scale effects on the propulsion performance of Joubert BB2 submarine with MARIN7371R propeller. Joubert BB2 submarine was designed as a realistic attack submarine to be used in benchmarking studies. Numerical analyses were conducted solving RANS equations. The propeller in the self-propelled case was modeled using the body force method. The numerical method was verified both for submarine and open water propeller cases. The resistance, open water propeller and propulsion characteristics were validated with the available numerical/experimental data. After, the results were extrapolated to the full-scale and compared with other studies. Full-scale RANS analyses were then conducted to calculate the resistance and propulsion parameters by eliminating the possible scale effects. The extrapolated full-scale results were compared with the full-scale analyses and self-propulsion method (SPE) results. The scale effects on the resistance and propulsion parameters were obtained in detail. 1978 ITTC prediction method coupled with the body force method was utilized to observe the scale effects. In addition to this, the practicality of the SPE method for the estimation of the propulsive performance was shown. The scale effects on the propulsive parameters such as nominal wake and thrust deduction factors, open water propeller efficiency and propulsion efficiency were seen

EFFECTS OF TEST PARAMETERS ON THE PRODUCTION OF HEXAGONAL BORON NITRIDE BY DCRN METHOD

conference paper at FunGlass School - part

Scale effect on ship resistance components and form factor

To design eco-friendly ships, the hydrodynamic behaviour of the hull has to be estimated precisely. The first and foremost one is the ship resistance, which is closely related to the energy efficiency of the ship. Different extrapolation methods, based on different assumptions, have been used to predict the full-scale ship resistance from model-scale experiments. In this manner, it is important to understand the scale effect on the individual ship resistance components. In this study, URANS CFD simulations of KCS and KVLCC2 were conducted at different scales. The total resistance components were decomposed into the individual resistance components to investigate the scale effects. The simulation results were compared with full-scale resistance predictions using different extrapolation methods and the rationale of the different compliances between them was investigated. Finally, the hydrodynamic characteristics in different scales were examined

Uncertainty assessment and self-propulsion estimation of Duisburg Test Case

In this study, hydrodynamic performance of Duisburg Test Case (DTC), a Post-Panamax container vessel, has been investigated by using Computational Fluid Dynamics (CFD) tools. Total resistance analyses have first been performed using an optimum grid number which has been determined by verification and validation processes based on Grid Convergence Index (GCI). Later, open water propeller analyses have been carried out by applying GCI for uncertainty approach. Finally, selfpropulsion analysis has been made for DTC hull by modelling the propeller using body force method for design speed. The major outcome of this study is to emphasize on the uncertainty assessment for calculating the ship’s total resistance and its open water propeller analyses. Additionally, the feasibility of body force method on self-propulsion performance prediction is discussed

Monoamines as Drug Targets in Chronic Pain: Focusing on Neuropathic Pain

Monoamines are involved in regulating the endogenous pain system and indeed, peripheral and central monoaminergic dysfunction has been demonstrated in certain types of pain, particularly in neuropathic pain. Accordingly, drugs that modulate the monaminergic system and that were originally designed to treat depression are now considered to be first line treatments for certain types of neuropathic pain (e.g., serotonin and noradrenaline (and also dopamine) reuptake inhibitors). The analgesia induced by these drugs seems to be mediated by inhibiting the reuptake of these monoamines, thereby reinforcing the descending inhibitory pain pathways. Hence, it is of particular interest to study the monoaminergic mechanisms involved in the development and maintenance of chronic pain. Other analgesic drugs may also be used in combination with monoamines to facilitate descending pain inhibition (e.g., gabapentinoids and opioids) and such combinations are often also used to alleviate certain types of chronic pain. By contrast, while NSAIDs are thought to influence the monoaminergic system, they just produce consistent analgesia in inflammatory pain. Thus, in this review we will provide preclinical and clinical evidence of the role of monoamines in the modulation of chronic pain, reviewing how this system is implicated in the analgesic mechanism of action of antidepressants, gabapentinoids, atypical opioids, NSAIDs and histaminergic drug

Passiflora incarnata attenuation of neuropathic allodynia and vulvodynia apropos GABA-ergic and opioidergic antinociceptive and behavioural mechanisms

Background: Passiflora incarnata is widely used as an anxiolytic and sedative due to its putative GABAergic properties. Passiflora incarnata L. methanolic extract (PI-ME) was evaluated in an animal model of streptozotocininduced diabetic neuropathic allodynia and vulvodynia in rats along with antinociceptive, anxiolytic and sedative activities in mice in order to examine possible underlying mechanisms. Methods: PI-ME was tested preliminary for qualitative phytochemical analysis and then quantitatively by proximate and GC-MS analysis. The antinociceptive property was evaluated using the abdominal constriction assay and hot plate test. The anxiolytic activity was performed in a stair case model and sedative activity in an open field test. The antagonistic activities were evaluated using naloxone and/or pentylenetetrazole (PTZ). PI-ME was evaluated for prospective anti-allodynic and anti-vulvodynic properties in a rat model of streptozotocin induced neuropathic pain using the static and dynamic testing paradigms of mechanical allodynia and vulvodynia. Results: GC-MS analysis revealed that PI-ME contained predominant quantities of oleamide (9-octadecenamide), palmitic acid (hexadecanoic acid) and 3-hydroxy-dodecanoic acid, among other active constituents. In the abdominal constriction assay and hot plate test, PI-ME produced dose dependant, naloxone and pentylenetetrazole reversible antinociception suggesting an involvement of opioidergic and GABAergic mechanisms. In the stair case test, PI-ME at 200 mg/kg increased the number of steps climbed while at 600 mg/kg a significant decrease was observed. The rearing incidence was diminished by PI-ME at all tested doses and in the open field test, PI-ME decreased locomotor activity to an extent that was analagous to diazepam. The effects of PI-ME were antagonized by PTZ in both the staircase and open field tests implicating GABAergic mechanisms in its anxiolytic and sedative activities. In the streptozotocin-induced neuropathic nociceptive model, PI-ME (200 and 300 mg/kg) exhibited static and dynamic anti-allodynic effects exemplified by an increase in paw withdrawal threshold and paw withdrawal latency. PI-ME relieved only the dynamic component of vulvodynia by increasing flinching response latency. Conclusions: These findings suggest that Passiflora incarnata might be useful for treating neuropathic pain. The antinociceptive and behavioural findings inferring that its activity may stem from underlying opioidergic and GABAergic mechanisms though a potential oleamide-sourced cannabimimetic involvement is also discussed

A NUMERICAL APPLICATION TO PREDICT THE RESISTANCE AND WAVE PATTERN OF KRISO CONTAINER SHIP

In this study, the computational results for KRISO Container Ship (KCS) are presented. CFD analyses are performed to simulate free surface flow around KCS by using RANS approach with success. Also the complicated turbulent flow zone behind the ship is well simulated. The RANS equations and the non-linear free surface boundary conditions are discretized by means of a finite volume scheme. The numerical methodology is found to be appropriate for simulating the turbulent flow around a ship in order to estimate ship total resistance and free surface. By the numerical results, total resistance is calculated for the ship model and the result is satisfactory with regard to the experimental one. As a result of well captured free surface, the wave elevation on/around the hull is compared with the experimental results

An investigation into the inhibitory function of serotonin in diffuse noxious inhibitory controls in the neuropathic rat

Background Following neuropathy α2-adrenoceptor-mediated diffuse noxious inhibitory controls (DNIC), whereby a noxious conditioning stimulus inhibits the activity of spinal wide dynamic range (WDR) neurons, are abolished, and spinal 5-HT7 receptor densities are increased. Here, we manipulate spinal 5-HT content in spinal nerve ligated (SNL) animals and investigate which 5-HT receptor mediated actions predominate. Methods Using in vivo electrophysiology we recorded WDR neuronal responses to von frey filaments applied to the hind paw before, and concurrent to, a noxious ear pinch (the conditioning stimulus) in isoflurane-anaesthetised rats. The expression of DNIC was quantified as a reduction in WDR neuronal firing in the presence of conditioning stimulus and was investigated in SNL rats following spinal application of (1) selective serotonin reuptake inhibitors (SSRIs) citalopram or fluoxetine, or dual application of (2) SSRI plus 5-HT7 receptor antagonist SB269970, or (3) SSRI plus α2 adrenoceptor antagonist atipamezole. Results DNIC were revealed in SNL animals following spinal application of SSRI, but this effect was abolished upon joint application of SSRI plus SB269970 or atipamezole. Conclusions We propose that in SNL animals the inhibitory actions (quantified as the presence of DNIC) of excess spinal 5-HT (presumed present following application of SSRI) were mediated via 5-HT7 receptors. The anti-nociception depends upon an underlying tonic noradrenergic inhibitory tone via the α2-adrenoceptor. Significance Following neuropathy enhanced spinal serotonin availability switches the predominant spinal 5-HT receptor-mediated actions but also alters noradrenergic signalling. We highlight the therapeutic complexity of SSRIs and monoamine modulators for the treatment of neuropathic pain