An iterative approach for obtaining nonlinear frequency of a conservative oscillator with strong nonlinearities

An iterative procedure is suggested for obtaining the higher-order approximate solutions of a conservative system comprising an oscillator with cubic and quintic restoring force function. The proposed method is similar to the traditional harmonic balance methods but unlike them the obtained from the previous step errors are considered in the present step to increase the accuracy of the solution. A comparison of results with those obtained by exact solution and other approximate analytical techniques confirms an accuracy of the method. It is shown that the achieved approximate solutions are valid for both small and large amplitudes of oscillation and can meet the exact solutions with a high level of accuracy in the lower-order of approximations. Furthermore, using the obtained analytical solutions, the effect of cubic and quintic terms on the frequency is discussed.Запропонована ітераційна процедура для отримання наближених розв’язків високого порядку консервативної системи, яка містить осцилятор з відновлювальною силою, що описується третім і п’ятим порядками нелінійності. Запропонований метод аналогічний до класичних методів гармонічного балансу, однак на відміну від них тут похибки, отримані на попередньому кроці, розглядаються на наступному кроці з метою підвищення точності розв’язку. Порівняння результатів з результатами, отриманими як точний розв’язок і іншими наближеними аналітичними методиками підтверджує точність методу. Показано, що отримані наближені розв’язки вірні як для малих, так і для великих амплітуд коливань і можуть узгоджуватись з точним розв’язком з високим рівнем точності при низьких порядках наближень. Далі обговорюється вплив членів третього і п’ятого порядків на основі отриманих аналітичних розв’язків

Performance index improvement of a double-pipe cooler with MgO/water-ethylene glycol (50:50) nano-suspension

A series of tests was conducted to unlock the potential application of MgO/water-EG (ethylene glycol) nanofluids (NF) in a double-pipe heat exchanger (HEX). The overall heat transfer coefficient (HTC), the inlet temperature of the working fluid, the fluid pressure drop (FPD), friction factor (FF) and the hydraulic performance index of the NF within the HEX were experimentally measured. Fouling of nanoparticles (NPs) within the Hex was also studied and modelled using asymptotic particulate fouling model. Results showed that MgO NPs can enhance the HTC by 39% at Re=10,500 and wt.% = 0.3 in the turbulent regime. Also, the presence of MgO NPs augmented the FF and the FPD values. The former was enhanced 33.8%, while the latter was augmented by 37% both at wt.% = 0.3 and at Reynolds number = 10,500. Results also revealed that the formation of porous particulate fouling layer on the internal wall of the inner tube creates a fouling thermal resistance which changes asymptotically with time. Overall, MgO/water-ethylene glycol shows a great potential to be used as a coolant within a HEX.H. Arya, M.M. Sarafraz, O. Pourmehran, M. Arjomand

Advancements in Acoustic Drug Delivery for Paranasal Sinuses: A Comprehensive Review

Available online 27 July 2023Chronic rhinosinusitis (CRS) impacts patients' quality of life and healthcare costs. Traditional methods of drug delivery, such as nasal sprays and irrigation, have limited effectiveness. Acoustic Drug Delivery (ADD) using a nebulizer offers targeted delivery of drug to the sinuses, which may improve the treatment of CRS. This review examines the influence of aerosol particle characteristics, aero-acoustic parameters, inlet flow conditions, and acoustic waves on sinus drug delivery. Key findings reveal that smaller particles improve the ADD efficiency, whereas larger sizes or increased density impair it. The oscillation amplitude of the air plug in the ostium is crucial for the ADD efficiency. Introducing acoustic waves at the NC-sinus system's resonance frequency improves aerosol deposition within sinuses. Future research should address advanced models, optimizing particle characteristics, investigating novel acoustic waveforms, incorporating patient-specific anatomy, and evaluating long-term safety and efficacy. Tackling these challenges, ADD could offer more effective and targeted treatments for sinus-related conditions such as CRS.Oveis Pourmehran, Kavan Zarei, Jeremie Pourchez, Sarah Vreugde, Alkis Psaltis, Peter-John Wormal

Heat transfer and pressure drop characteristics of MgO nanofluid in a double pipe heat exchanger

The present work aims to investigate the plausible application of MgO-ethylene glycol as a heat transfer fluid in a double-pipe heat exchanger. The nanofluid was prepared using a two-step method at weight concentrations of 0.1, 0.2 and 0.3%. The test rig provided conditions to measure the convective heat transfer coefficient, pressure drop and friction factor of the system. Influence of the different operating parameters such as flow rate, mass concentration of nanoparticles and inlet temperature of nanofluid to the heat exchanger on the heat transfer coefficient and pressure drop was experimentally investigated. Results showed that the heat transfer coefficient within the heat exchanger can be enhanced by 27% for wt.% = 0.3 in comparison with the base fluid (ethylene glycol). It was also found that the presence of MgO nanoparticles increased the pressure drop by 35% at wt.% = 0.3. The friction factor of the system decreased nonlinearly with an increase in the Reynold number and it followed the trend of 64/Re equation. An increase in the mass concentration of nanoparticles increased the friction factor and the maximum friction factor enhancement was 32% belonging to the nanofluid with mass concentration of wt.% = 0.3. Likewise, inlet temperature was found to have a very slight influence on the heat transfer coefficient and no effect on the friction factor and pressure drop of the system. The thermo-physical properties of MgO-ethylene glycol nanofluid was also experimentally measured at various temperatures.H. Arya, M.M. Sarafraz, O. Pourmehran, M. Arjomand

Acoustically-driven drug delivery to maxillary sinuses: aero-acoustic analysis

This paper investigates the effect of aero-acoustic parameters on the efficiency of acoustically-driven drug delivery (ADD) to human maxillary sinus (MS). To be more specific, the effect of the frequency, amplitude at the acoustic excitation, and the inlet mean flow rate on the efficiency of ADD to the MS is studied. Direct computational aero-acoustics, using a validated computational fluid dynamics (CFD) model, has been utilised to carry out the parametric study. The transport pattern of the particles (drugs) in the presence of an external acoustic field has been investigated through the discrete phase model. Extensive computational simulations have revealed that the most important parameter in acoustically-driven drug delivery to the MS is the amplitude of the oscillation of the air plug in the ostium, which is largest when the combination of nasal cavity and MS is at resonance. Also, it has been found that the amplitude of the inlet acoustic wave has a direct correlation with the efficiency of the drug delivery to the MS. Moreover, the inlet mean airflow rate adversely affects the efficiency of the drug delivery to the MS. The results of this study suggest that applying an external acoustic field after distributing the drug particles with no mean flow results in a better drug delivery than in the presence of an inlet mean flow.Oveis Pourmehran, Benjamin Cazzolato, Zhao Tian, Maziar Arjomand

Statistical optimization of microchannel heat sink (MCHS) geometry cooled by different nanofluids using RSM analysis

In this work, an analytical investigation of the heat transfer for the microchannel heat sink (MCHS) cooled by different nanofluids (Cu, Al2O3, Ag, TiO2 in water and ethylene glycol as base fluids) is studied by the porous media approach and the Galerkin method and results are compared with numerical procedure. Response surface methodology (RSM) is applied to obtain the desirability of the optimum design of the channel geometry. The effective thermal conductivity and viscosity of the nanofluid are calculated by the Patel et al. and Khanafer et al. model, respectively, and MCHS is considered as a porous medium, as proposed by Kim and Kim. In addition, to deal with nanofluid heat transfer, a model based on the Brownian motion of nanoparticles is used. The effects of the nanoparticles volume fraction, nanoparticle type and size, base fluid type, etc., on the temperature distribution, velocity and Nusselt number are considered. Results show that, by increasing the nanoparticles volume fraction, the Brownian movement of the particles, which carries the heat and distributes it to the surroundings, increases and, consequently, the difference between coolant and wall temperature becomes less

An analytical investigation on unsteady motion of vertically falling spherical particles in non-Newtonian fluid by Collocation Method

An analytical investigation is applied for unsteady motion of a rigid spherical particle in a quiescent shear-thinning power-law fluid. The results were compared with those obtained from Collocation Method (CM) and the established Numerical Method (Fourth order Runge–Kutta) scheme. It was shown that CM gave accurate results. Collocation Method (CM) and Numerical Method are used to solve the present problem. We obtained that the CM which was used to solve such nonlinear differential equation with fractional power is simpler and more accurate than series method such as HPM which was used in some previous works by others but the new method named Akbari-Ganji’s Method (AGM) is an accurate and simple method which is slower than CM for solving such problems. The terminal settling velocity—that is the velocity at which the net forces on a falling particle eliminate—for three different spherical particles (made of plastic, glass and steel) and three flow behavior index n, in three sets of power-law non-Newtonian fluids was investigated, based on polynomial solution (CM). Analytical results obtained indicated that the time of reaching the terminal velocity in a falling procedure is significantly increased with growing of the particle size that validated with Numerical Method. Further, with approaching flow behavior to Newtonian behavior from shear-thinning properties of flow (n → 1), the transient time to achieving the terminal settling velocity is decreased