Question

If the first-order implicit Euler scheme is used, the value at t+Δt/2 is replaced by the value at _________

(a) t

(b) t-(frac{Delta t}{2})

(c) t+Δt

(d) t-Δt

Answer 1

The correct choice is (c) t+Δt

To explain: In the first-order implicit Euler scheme, the values at the cell faces are approximated by the values at cell centres of the backward direction. Therefore, the value at t+(frac{Delta t}{2}) is replaced by the value at t.