title: Theoretical and experimental investigation of fluid rheology effects on modulated ultrasound propagation.
abstract: A mathematical model is developed and presented to capture the effect of viscoelastic nature of a material on modulated ultrasound (US) pulses. The model is established by considering perturbation of material elements subject to modulated US pulses and by introducing the exponential relaxation of the perturbed fluid elements with a spectrum of time constants. Both the model and experimental findings revealed that consecutive perturbation of a material via the modulated US pulses enabled to probe the relaxation times of similar order of magnitudes to the frequency of the US modulation while filtering out the impact of other relaxation times on the US measurement. The US experimental results were verified by those of a conventional rheometer. Hence carrying out measurements at different US modulation frequencies in the Hz ranges seems to allow one to obtain the relaxation time spectrum of the investigated material in the time scales of milliseconds to seconds.
authors.affiliation: Department of Chemical Engineering, Middle East Technical University, 06800 Ankara, Turkey.
authors.forename: Okan
authors.initials: O
authors.lastname: Özkök
authors.affiliation: Department of Chemical Engineering, Middle East Technical University, 06800 Ankara, Turkey. Electronic address: yuludag@metu.edu.tr.
authors.forename: Yusuf
authors.initials: Y
authors.lastname: Uludag
mesh_terms: D002266:Carboxymethylcellulose Sodium / Q000737:chemistry*; D003198:Computer Simulation; D004548:Elasticity; D008962:Models, Theoretical; D012212:Rheology / Q000295:instrumentation / Q000379:methods*; D014465:Ultrasonics; D014783:Viscosity
chemical_list: D002266:Carboxymethylcellulose Sodium
keywords: Fluid rheology; Modulated sound signal propagation; Relaxation time; Ultrasonic characterization techniques; Viscoelasticity