If you want to start multiple nodes on the same machine (for tests purposes) just run:
bin/elasticsearch -Epath.data=data1 -Epath.logs=log1
bin/elasticsearch -Epath.data=data2 -Epath.logs=log2
bin/elasticsearch -Epath.data=data3 -Epath.logs=log3
Without changing anything in the default elasticsearch.yml and you should be done.