Questions tagged [dae]
A (system of) Differential Algebraic Equations (DAE) is a system of equations with ordinary differential equations and algebraic equations; all the equations should be satisfied simultaneously.
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Choice between DAE or ODE formulation for chemical systems
Consider a simple ODE system describing the evolution of two chemical species undergoing the reaction $A = B$ :
$$ \frac{dn_A}{dt} = - k * n_A $$
$$ \frac{dn_B}{dt} = k * n_A $$
We can discretize ...
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0
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SUNDIALS using Python Interface tutorial
I am attempting to solve differential algebraic equations using SUNDIALS with a Python interface. I am having trouble learning to actually use sundials, and cannot seem to find any tutorials online ...
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1
answer
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solving a Algebraic Differential Equation in Julia using modelingToolKit.JL
I'm trying to solve a differential algebraic equation in Julia's modelingTookKit.JL, where the vector field has the form f(X) = 0.
I found an example of a DAE in the below link
modelingToolkit.JL DAE](...
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2
votes
1
answer
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Index reduction of a DAE from a PDE system
I have a system of 2 non-linear, coupled PDEs that I would like to transform to a stiff ODE system to solve them using the method of lines. The 2 equations:
$$\begin{align}
\frac{\partial \phi}{\...
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1
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Solving DAE in Julia using GPUs
I'm trying to solve a Differential Algebraic Equation (DAE) in Julia which is very computationally expensive using GPUs. I'm brand new to Julia and don't have much experience coding with GPUs. The ...
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2
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0
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Problem with Numerical DAE Implementation of Nernst-Planck Equations
I write to you all today in order to clarify if I implemented my model correctly into MATLAB.
I will outline the following: analytical governing equations, my discretization for the equations and ...
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"This DAE appears to be of index greater than 1" daeic12 (line76) error code
Hi I am trying to solve a set of pde converted into ODE and DAE using central finite difference method. I have used the MATLAB 'solve' command to determine the coefficients of fictitious nodes for ...
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Problem with solving coupled ODE and DAE equations with mass matrix (Error using daeic12 (line 77) This DAE appears to be of index greater than 1)
I am trying to solve 6 ODE equations coupled with 1 DAE one. The ODE equations have been discritized in space domain and ode15s MATLAB solver is used to solve the equations in time domain. I have ...
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How to increase the stability of a DAE solver?
I am trying to solve a set of linear PDEs of the form
$$F\left(\vec{y},\frac{\partial \vec{y}}{\partial x},\frac{\partial^2 \vec{y}}{\partial x^2},\frac{\partial \vec{y}}{\partial t}\right)=0.$$
To ...
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Optimality conditions for optimal control: BVP - DAE
I am solving an optimal control problem of the form
$$
\min_u \qquad\int_0^T \langle u(t), u(t) \rangle \, \mathrm{d}t \\
s.t. \quad \dot{x} = \tilde{f}(x) + u, \quad x(0)=x_0 \\
\qquad \tilde{\Phi}(...
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How to solve an implicit ODE with forward Euler?
Consider the implicit ODE
$$
M(y)\dot{y} = F(t,y)
$$
If $M$ is non-singular for all $y$
How to use the forward-Euler method to numerically solve for $y$ without inverting $M(y)$?
I only came out ...
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Procedure to identify characteristic properties of unknown functions in a DAE model
I have a system of 1st order odes given by
$$
\dot{x_1}(t) = \alpha_1 f_1(x_1,t) + \beta_1 u(t) \\
\dot{x_2}(t) = \alpha_2 f_2(x_2,t) + \beta_2 u(t)
$$
They are constrained by an algebraic equation
...
1
vote
1
answer
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Open source solver for continuous-time stochastic non-linear DAEs (SDAEs)
I am trying to solve a system of non-linear index-1 DAEs in which the derivatives of the state variables, $x(t)$ are corrupted by additive noise, $w(t)$ (whose covariance matrix is known).
$\dot x(t) =...
0
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1
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DAE in Matlab: ode15s
I have to solve this problem
$$\left\{\begin{matrix}
y''=4y'+\frac{1}{h}-7y\\
y(1)=1\\
y'(1)=1
\end{matrix}\right. \text{where} \; h=5y'-2y$$
as it were a DAE (I know I could just substitute $h$ ...
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3
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Choice of solver/software for global optimisation of cheap black-box function with known derivatives
I am trying to estimate a few unknown parameters of my continuous non-linear PDAE model (simulated through finite-volume method spatial discretisation, and time-stepping through method-of-lines). I am ...
1
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1
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Does anyone have a driver for fortran DAE solver - COLDAE?
Coldae is a solver writter by U Ascher and R Spiteri, located here http://www.cs.ubc.ca/~ascher/coldae.f .
It can solve upto index-2 DAEs using collocation.
I am new to Fortran, and having a hard ...
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ODEs vs DAE vs ADE?
I am totally confused between ODEs which I am familiar with, and differential algebraic equations (DAE) and algebraic differential equations (ADE). Are they the same but just different names or what ...
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Solving DAE with higher index
I want to solve 7 coupled differential equations in MATLAB. I used the method of lines (MOL) to convert them to a system of DAEs. I then attempted to solve this system using ode15s. Unfortunately an ...
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