Thanks for the clarification.
My purpose is to concatenate the entire tensors of channel with the half-size W and H array. (I will not use pooling operation) To be specific, if the shape of tensor is ([16(C), 112(W),112(H)]), then I firstly downscale only the H and W, and then want to combine with C. So it will be ([16,56,56]).
For this purpose,  should I flatten them individually and then reshape it ?? since the array[:, channel_number, :, :] will give me a specific channel tensor instead of whole.