In some aspects, locations for nodes are computed for a one-dimensional flow model that models well system fluid flow in a subterranean region. Truncation error threshold data indicate a truncation threshold value for each of the nodes. Discretization data indicate a lowest-order term truncated from a discretized governing flow equation for each of the nodes. The locations for the nodes can be computed based on a scalar cost function, such that each of the lowest order terms is less than or equal to the truncation error threshold value for the respective node.