58 Questions 134 Answers 0 Followers
Questions related from Abdallah Daddi-Moussa-Ider
Using the singularity method, the primary fundamental solution (stokeslet) associated with a point force is obtained. The particle mobility for a spherical particle can be found after integrating...
12 December 2015 8,626 3 View
In a hydroelasticity problem, I have used the temporal Fourier transform in order to solve the linear hydrodynamic equations. The system of interest consists of a solid particle moving close to an...
05 May 2015 9,015 1 View
Let us consider a spherical particle of radius a, moving inside a viscous fluid in the low Reynolds number regime. After solving the Stokes equations in Fourier space, for a time dependent point...
04 April 2015 5,692 2 View
It is well known that corners require a special treatment in the 2D boundary integral equaiton. The factor 1/(2pi) appearing in the equation should be replaced by 1/(2 alpha), where alpha is the...
01 January 2015 9,795 6 View
I would like to know whether exact analytical solutions exist for the fluid flow between two planes with a linearly increasing height, when the convective term is zero (please see the attached...
01 January 2015 9,244 8 View
I would like to solve a system of equations for a relatively large matrix dimension (around 300 times 300). The matrix is full of zeros and several of the iterative methods that I used didn't...
12 December 2014 6,279 17 View
Hello, The PDF P(r,t) of finding a pair of particles at a given separation r at a later time t is known. Also, the PDF P(k,r) of finding this pair at a given rotation k when it reaches a given...
11 November 2014 4,546 10 View
The velocity of each node in a spherical mesh is known instantaneously. I would like to characterize the velocity of the whole object knowing that it is allowed to rotate during its motion. How...
09 September 2014 1,868 10 View
It is well known that particles suspended in a Newtonian fluid are exposed to random forces. These forces are at the origin of diffusive (Brownian) motion of these particles and they are caused by...
08 August 2014 7,761 14 View
Boundary integral formulations are considered as robust and efficient methods used to solve the linearized Navier-Stokes equation. The partial differential equations are transformed into integral...
08 August 2014 7,069 4 View
I would appreciate it if someone could point me to one paper or two in which the resistance problem is treated using the CDLBIEM. What I found in the literature is just a description of the...
08 August 2014 9,935 1 View
The PDF of a given vectorial quantity modulus is known. I would like to obtain the PDF of each of the three vector components in the case of isotropy, i.e. the three PDFs are supposed to be equal....
06 June 2014 4,184 16 View
I would like to fit numerical results obtained by NDS of the high order moments of the transverse velocity increment using a generalization of Batchelor parametrization together with a...
06 June 2014 4,652 2 View
I would appreciate if someone here could suggest some papers concerning the application of the MF formalism on the transverse Eulerian velocity structure function. I have found indeed several...
06 June 2014 5,569 1 View
My random variable of interest is the ratio of a Gaussian normal distributed variable and a Richardson self similar distribution. These two variables are independent. Is it possible to get an...
05 May 2014 9,263 1 View
It is of major interest to find out the two-time Lagrangian autocorrelation function of a given property A. This function has generally a decaying behavior giving a characteristic correlation time...
05 May 2014 3,847 4 View
For a given random variable, I have performed a series of calculations and noticed that the kurtosis evolves linearly with respect to the square of skewness. My purpose here is to find out a two...
05 May 2014 5,546 9 View
The eddy-diffusivity for a single particle in turbulent flow if defined as half the time derivative of the mean squared displacement measured from the origin. For the separating pairs, it is...
05 May 2014 5,632 2 View
I am new to multifractal models used in turbulence in order to characterize the intermittency behavior neglected by the Kolmogorov picture and I have a trouble with some basic notions. Could...
05 May 2014 9,097 3 View
The intermittency of the Eulerian velocity increment is a characteristic of the downward energy cascade in 3D turbulence. In the inertial range and using Kolmogorov second similarity hypothesis,...
05 May 2014 2,648 2 View
I use usually the software paint in order to draw or adapt figures of experiments and create explicative schematics. However, I think that it is not too technical and I am looking for a free...
04 April 2014 7,510 12 View
The size of an linear object constituted by 2 vertex points is the length of the line segment joining these two points. For three points, we may define the radius of gyration or maybe the square...
04 April 2014 7,650 21 View
I have a set of trajectories of three particles and their instantaneous velocities. I would like to compute the 3 components of the angular velocity pseudovector of the fictive triangle formed by...
04 April 2014 5,883 13 View
One important way to characterize turbulent flow is by evaluating the Eulerian longitudinal velocity structure function. Deviations from the behavior predicted by the Kolmogorov theory are...
04 April 2014 1,354 1 View
The diffusive approach of the Richardson model (1926) for separating particle pairs fails to describe faithfully the real dynamics in 3D turbulence. Such a model requires a fast decorreation in...
04 April 2014 7,631 2 View
White blood cells (WBCs) are part of our immune system, performing various organism defense functions. In order to reach the sites of action, they have to migrate to the vessel walls through a...
04 April 2014 9,946 10 View
The motion of a single small ellipsoidal body immersed in a Newtonian fluid is governed by the equation given by Jeffery (1922), where the inertia and Brownian rotation are neglected. This...
04 April 2014 9,303 1 View
One of the fundamental features of fully developed 3D turbulence is the non-Gaussian statistics at small scales. The energy transfer from the largest scales toward the smallest scales is related...
04 April 2014 7,486 1 View
The flow of blood inside the vessels is a non trivial fluid dynamics problem since particles with different size, shape and inertia are involved. In a simplest way, the fluid phase of the blood,...
04 April 2014 5,250 4 View
In recent years, considerable research efforts have been devoted to new types of microscopic biomedical devices. A prominent example is nanoparticles which are injected into the blood stream for...
04 April 2014 1,299 2 View
DNS is a the best way to solve the dynamics equations since all turbulent scales are resolved adequately. A compete description of the fluid flow can nicely be obtained but unfortunately just for...
03 March 2014 3,052 10 View
Given a pair of particles released at time t = 0 from a localized source. I would like to study the evolution of the mean-squared-angular velocity with respect to time for a given separation (for...
03 March 2014 5,479 6 View
Diffusion is considered to be one of the most important transport phenomena in nature. It is defined as a macroscopic behavior emerging at long times from many different microscopic ones....
03 March 2014 1,474 16 View
I have found that the component PDFs of a given vectorial quantity have the same exponential distribution. I am also interested in the PDF of the modulus (please see the picture enclosed). Is it...
03 March 2014 6,937 18 View
Given a probability density function supported on a semi-infinite interval obtained numerically. What is the best methodology to follow in order to know / estimate the distribution law (Beta...
03 March 2014 8,313 9 View
The particle dynamics can be obtained by solving the particle equation coupled to the Navier-Stokes equations for the fluid with no-slip boundary condition on the particle’s surface. However,...
03 March 2014 1,161 0 View
Generally in experiments and/or in numerical simulations, the turbulence level of a fluid flow is reported by the Reynolds number based on the Taylor microscale, which its square, in homogeneous...
03 March 2014 9,635 23 View
Turbulence is a phenomenon that we experience in our every day life. Understanding turbulent flow remains a challenge for both theory and experiment. Turbulence occurs when the viscous forces in a...
03 March 2014 9,051 1 View
The relative diffusion of two particle pairs was first investigated by Richardson in a pioneer paper written in 1926. His model allowed to describe the mean squared separation with respect to time...
03 March 2014 2,144 4 View
Is it possible to produce good trajectories of advected fluid particles and then make accurate statistical analysis of the Lagrangian dynamics without basing on the Eulerian field of a given...
02 February 2014 8,250 1 View
Recently the focus in turbulence is shifted to the study of shape evolution. Staring from regular shapes at the Kolmogorov dissipative scale, one wants to characterize the geometrical evolution...
02 February 2014 520 11 View
Are there any numerical advantages of the vorticity equation over the original momentum equation in the study of 2D incompressible flows?
02 February 2014 9,066 4 View
I would like to plot the variations of the kinetic energy with respect to the wavenumber for the 2D Taylor Green vortices. I obtained numerically the form shown below but I am not sure if it has a...
02 February 2014 1,327 13 View
Second viscosity effect on Newtonian compressible flows.
01 January 2014 1,806 9 View
The Maxey-Riley-Gatignol Equation (1983) describes the behavior of a spherical rigid particle carried by a fluid. The dispersed phase dynamics is generally modeled by this lagrangian approach...
01 January 2014 3,925 3 View
In the course of turbulent mixing we saw that Langevin set a stochastic model to describe the behavior of a pollen particle in the presence of a viscous force and a random force. What does it mean...
01 January 2014 7,956 21 View
There are many numerical schemes devoted to solving the equation of motion in fluid mechanics such as FDM and FVM. The spectral method is also widely used by researchers who seek more accuracy and...
01 January 2014 5,096 22 View
Since the total mass of a Dirac function is unity, can it be a PDF of a given random variable?
01 January 2014 6,248 23 View
The flame is propagating from the right (burnt gases) to the left (unburned gases). The Dirac delta function models the heat release in the reaction zone at x = 0 and d represents the flame...
01 January 2014 5,456 6 View
As proved experimentally, it is possible to maintain a laminar flow in a pipe flow for high Reynolds numbers, e.g., Salwen et al. (1980) and, in particular, Meseguer & Trefethen (2003), who...
12 December 2013 6,835 3 View
Bifurcation theory provides models of transitions and instabilities as some control parameter is varied. One of the most important types of bifurcation is the pitchfork bifurcation observed in...
12 December 2013 2,991 5 View
It is well known that pipe Poiseuille flow undergoes transition to turbulence for Re on the order of 2,000. How about a plane Poiseuille flow?
11 November 2013 955 14 View
How can a given flow be embedded in a family of other flows in the aim of visualizing the 3D stationary states?
11 November 2013 1,441 0 View
The Korteweg-de Vries equation is a mathematical model to describe waves in shallow water approximation, and can be integrated analytically to give an exact solution. Which kind of information can...
11 November 2013 5,868 4 View
I read in Wikipedia (Peregrine soliton) that the NLS equation is written for deep water. Is it legitimate to use this mathematical description for shallow water? What do we mean by an anomalous...
11 November 2013 5,684 1 View
Is it legitimate to consider that a given system at equilibrium is self-organized?
11 November 2013 8,432 13 View
I would like to know please if there is a restriction in the application of the Hagen–Poiseuille solution.
11 November 2013 10,048 11 View
We saw in the turbulence class that the right region of the Lumley diagram which is called the axisymmetric in cigar, includes flows such as boundary layer of jet flow. Are there any similarities...
11 November 2013 645 8 View
